The Form 424A Files Dataset collects EDGAR filings of Form 424A — the pre-effective preliminary prospectus filed under Rule 424(a) of the Securities Act of 1933 when an issuer makes substantive changes or additions to a prospectus previously filed as part of a still-pending registration statement (S-1, S-3, S-4, S-11, F-1, F-3, F-4, or related forms). Each record corresponds to one EDGAR filing, identified by an SEC accession number, and bundles a structured metadata.json together with the original prospectus document and any non-image exhibits from the original submission. The filer is always the issuer-registrant of the underlying registration statement, and the filing obligation is event-driven: the document must be on EDGAR no later than the date the substantively revised pre-effective prospectus is first sent or given to any prospective investor. Coverage begins with the earliest sample date of 1994-01-01 and continues through the present, with monthly ZIP containers refreshed as new 424A filings hit EDGAR. Because most subsequent prospectus updates flow through Rule 424(b) variants instead, Form 424A is a comparatively rare filing type and the dataset is correspondingly compact.
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The Form 424A Files dataset packages every EDGAR submission tagged with form type 424A from 1994 through the present. The underlying filing is a near-complete preliminary prospectus, generally indistinguishable in structure from a full S-1 prospectus body but carrying the Rule 424(a) cover-page legend and the file number of the underlying registration statement (typically a 333--prefixed Securities Act file number). Form 424A is filed when an issuer-registrant disseminates a substantively revised pre-effective prospectus while the registration statement is still pending; once the registration statement is declared effective, further prospectus updates move out of 424(a) and into the Rule 424(b) regime.
The dataset is distributed as one ZIP container per calendar month. Each container holds one folder per accession, named with the 18-digit dash-stripped accession number, containing a metadata.json and the original EDGAR submission documents. Referenced graphics (JPG, GIF) are deliberately excluded from the ZIP but remain enumerated in the metadata with direct EDGAR URLs for retrieval. The file types found in the dataset are TXT, JSON, HTML/HTM, and PDF.
A single record in the Form 424A Files dataset corresponds to one EDGAR filing of Form 424A, identified by a unique SEC accession number. Within the dataset's monthly ZIP containers, that record materializes as a folder named after the accession number with dashes removed (an 18-digit, zero-padded string such as 000119312525122548). Each accession folder bundles together a structured metadata.json describing the filing and the original EDGAR submission documents, with referenced image files (JPG, GIF) intentionally excluded.
The unit of observation is the filing, not the issuer or the offering. A single registration statement gives rise to a Form 424A filing only when substantive changes to a previously filed prospectus need to be made before effectiveness; an issuer engaged in multiple distinct offerings may produce multiple records over time.
The dataset is distributed as one ZIP per calendar month. The container hierarchy is:
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form-424a-files/<year>/<year>-<month>.zip
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└── <year>-<month>/
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└── <accession-no-without-dashes>/
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├── metadata.json
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└── <primary 424A document>.htm (or .txt / .pdf for older filings)
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└── <additional non-image documents, if any>
Key conventions:
metadata.json is always present.metadata.json.Form 424A is a prospectus filing made under Rule 424(a) of the Securities Act of 1933. It is used to file a pre-effective prospectus that contains substantive changes from, or substantive additions to, a prospectus that was previously filed as part of a registration statement (typically a Form S-1, Form S-3, Form S-4, Form F-1, Form F-3, Form F-4, or related registration form). Rule 424(a) requires the amended prospectus to be filed no later than the date it is first sent or given to any person prior to the effective date of the registration statement. Because most subsequent prospectus updates flow through Rule 424(b) variants instead, Form 424A is a comparatively rare filing type, which is reflected in the dataset's modest cumulative volume since 1994.
The underlying document is therefore a near-complete preliminary prospectus, generally indistinguishable in structure from a full S-1 prospectus body but carrying the Rule 424(a) cover-page legend and the file number of the underlying registration statement (typically a 333--prefixed number).
Every record is composed of two layers:
metadata.json. It captures filing identifiers, EDGAR links, the inventory of submitted documents, and the filer/registrant party data.metadata.json is the structured anchor of every record. Its top-level fields are:
formType — always "424A" for this dataset.accessionNo — the EDGAR accession number with dashes (e.g., 0001193125-25-122548); the folder name is the same value with dashes stripped.description — human-readable form description, e.g., "Form 424A - Prospectus [Rule 424(a)]".filedAt — ISO-8601 timestamp with timezone offset capturing when EDGAR accepted the filing.linkToFilingDetails — URL of the primary document on EDGAR (typically the prospectus HTM).linkToTxt — URL of the full SGML submission text bundle on EDGAR.linkToHtml — URL of EDGAR's filing index page for this accession.linkToXbrl — URL to an XBRL instance, if any. Form 424A filings do not carry XBRL, so this field is consistently an empty string.id — opaque internal identifier (MD5-style hash) for the record.documentFormatFiles[] — array enumerating every document in the original EDGAR submission.dataFiles[] — array of XBRL or other structured data files; consistently empty for Form 424A.seriesAndClassesContractsInformation[] — used by investment-company filings; consistently empty for Form 424A.entities[] — array of filer/registrant parties associated with the submission.documentFormatFiles[]Each entry describes one component of the original EDGAR submission with the fields:
sequence — 1-based string; blank for the master submission TXT bundle.size — bytes as a string.documentUrl — direct EDGAR URL of the document.description — e.g., "424A", "GRAPHIC", "Complete submission text file".type — e.g., "424A", "GRAPHIC".A typical 424A submission's documentFormatFiles[] therefore enumerates the primary 424A HTM, any non-image exhibits, every referenced graphic (each as a GRAPHIC entry), and the per-submission "Complete submission text file" SGML bundle. Entries with type "GRAPHIC" remain present even though the corresponding image files are excluded from the ZIP, so the metadata always reflects the complete original submission inventory and exposes URLs for retrieval from EDGAR if needed.
entities[]Each entry describes a registrant or filer party with the fields:
cik — SEC Central Index Key.companyName — filer name with role suffix in parentheses, e.g., "... (Filer)".fileNo — SEC file number, typically the 333--prefixed Securities Act registration file number.filmNo — EDGAR film identifier for the submission.act — Securities Act code, "33" for the Securities Act of 1933.type — filer role/type code, generally "424A" for the principal filer.sic — Standard Industrial Classification code with description.stateOfIncorporation — two-letter state or jurisdiction code.fiscalYearEnd — MMDD string.tickers — array of ticker symbols where applicable.entities[] may carry more than one entry — for example, a parent issuer plus a guarantor subsidiary, or co-registrants in a debt offering — with each companyName suffix identifying the party's role.
The primary document in a Form 424A submission is the prospectus itself. The filename follows EDGAR's convention, typically d<filer-doc-id><form-suffix>.htm (for example, d913698d424a.htm). Modern filings open with the SGML document envelope:
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<DOCUMENT>
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<TYPE>424A
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<SEQUENCE>1
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<FILENAME>d913698d424a.htm
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<DESCRIPTION>424A
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<TEXT>
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<HTML> ... full prospectus body ... </HTML>
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</TEXT>
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</DOCUMENT>
Inside <TEXT>...</TEXT> sits full-fidelity HTML containing the body of the prospectus, with inline CSS, heavily styled tables, anchor-based intra-document navigation (table-of-contents anchors, item anchors), and <IMG> references that point to graphics on EDGAR (which are not bundled in the dataset).
Internally, the prospectus follows the conventional structure of an SEC-registered offering document. The principal sections appear in roughly this order:
The narrative is interleaved with substantial tabular content — capitalization tables, dilution tables, beneficial ownership tables, summary financial tables, and the underwriting allocation table — all rendered as HTML tables within the body.
Although Form 424A submissions are usually dominated by the prospectus document itself, the original EDGAR submission may include additional non-image exhibits. When present, these appear inside the accession folder alongside metadata.json and the primary prospectus, and they are also enumerated in documentFormatFiles[]. The same array also lists the per-submission "Complete submission text file" (the EDGAR-generated SGML bundle for the entire submission) and any GRAPHIC entries (JPG, GIF) referenced by the HTML. Graphics are excluded from the ZIP per the dataset's image-exclusion policy but remain reachable via the URLs in the metadata.
A complete record contains:
metadata.json file with form identifiers, EDGAR links, the document inventory, and entity/registrant information.The dataset deliberately excludes image files referenced by the prospectus (JPGs, GIFs, and similar binary graphics). These remain enumerated in documentFormatFiles[] so they can be retrieved directly from EDGAR via the documentUrl value, but they are not unpacked into the accession folder. The dataset also does not redistribute EDGAR's separate filing index page; that resource is referenced through linkToHtml. Because Form 424A filings do not carry XBRL, the dataFiles[] array is consistently empty and linkToXbrl is an empty string — there are no XBRL instance documents, schemas, or linkbases to include.
The substantive disclosure content of a Form 424A prospectus tracks the disclosure regime of the underlying registration form (most commonly Form S-1 or S-3). Several rule changes have materially affected what a Form 424A prospectus typically contains across the 1994-to-present span of the dataset:
Form 424A filings have evolved through the same EDGAR format generations as other Securities Act prospectus filings:
<DOCUMENT>...<TEXT>...</TEXT></DOCUMENT> envelope. PDF copies sometimes accompanied the HTM as supplementary documents.The metadata layer (metadata.json) is a stable JSON structure applied uniformly across the dataset, regardless of the underlying document era.
Several nuances matter for working with these records:
metadata.json.accessionNo carries the canonical dashed form.<TEXT> and stop at </TEXT>, or otherwise strip the wrapper. The same applies to exhibits.<IMG> references inside the prospectus HTML resolve to URLs on EDGAR, not to local files in the folder. The documentFormatFiles[] entries with type "GRAPHIC" provide direct URLs for retrieval if needed.entities[] may include more than one party — for example, a parent issuer and a guarantor subsidiary, or a co-registrant in a debt offering. Each entry's companyName carries a role suffix in parentheses identifying its relationship to the filing.fileNo value on each entities[] entry (a 333--prefixed Securities Act file number) ties the 424A back to its parent registration statement and is the most reliable join key for connecting a 424A to the underlying S-1/S-3/S-4 family of filings.The filer is the issuer-registrant of a Securities Act of 1933 registration statement that is on file with the SEC but not yet effective. The 424A is not a standalone registration; it is a prospectus document filed against an existing pre-effective registration statement (typically Form S-1, S-3, S-4, S-11, F-1, F-3, or F-4) by the same legal entity that signed and submitted that registration statement.
The reporting population covers Securities Act registrants in the pre-effective window, including:
The filer is always the registrant. Underwriters, selling shareholders, and other parties named in the prospectus do not file the 424A in their own capacity even when they drive its content.
Form 424A is filed under Rule 424(a) under the Securities Act of 1933, which governs the filing of pre-effective prospectuses that contain substantive changes from or additions to a prospectus previously filed as part of the registration statement. Rule 424(a) operates inside the Securities Act offering framework set by:
A 424A is therefore a pre-effective preliminary prospectus under Section 10(b), filed as a separate EDGAR submission rather than as an amendment to the registration statement itself.
The trigger is distribution-driven, not periodic. Rule 424(a) requires the filing no later than the date the substantively revised prospectus is first sent or given to any person while the registration statement is still pending. The filing obligation arises the moment the registrant, an underwriter, or any agent first delivers the updated preliminary prospectus to a prospective investor, roadshow participant, or other recipient.
Substantive changes that typically trigger a 424A include:
The deadline is event-driven and contemporaneous: the document must be on EDGAR no later than the date of first dissemination of the substantively revised pre-effective prospectus. There is no fixed business-day clock and no periodic schedule.
A single registration statement can produce multiple 424A filings as the preliminary prospectus is iterated and re-circulated before pricing; each new substantive version that is sent or given to any person creates a fresh Rule 424(a) obligation. Once the registration statement is declared effective, further prospectus updates move out of 424(a) and into the Rule 424(b) regime.
Rule 424 defines a family of prospectus-filing categories. The key distinction is timing relative to effectiveness: 424A is the pre-effective variant; the 424(b) sub-paragraphs are post-effective.
A registrant disseminating a substantively updated preliminary prospectus before effectiveness files under 424(a); the same registrant files updates under the appropriate 424(b) paragraph after effectiveness.
Each record in this dataset therefore corresponds to a discrete pre-effective prospectus dissemination event tied to a specific Securities Act registration statement, with the issuer-registrant as the EDGAR filer and Rule 424(a) as the governing trigger.
Form 424A sits in a tightly clustered family of Securities Act prospectus and registration filings. Most neighbors share issuers, document text, and even file-cluster timing. They diverge on three axes: (1) whether they are filed pre- or post-effectiveness, (2) what triggers the filing, and (3) whether the document is a standalone prospectus, a registration statement, or a non-statutory communication.
Rule 424(b) prospectuses (Form 424B1–B8). The post-effective siblings of 424A. A 424A is filed before effectiveness and reflects substantive changes that, under Section 8(a), restart the 20-day waiting period. The 424B variants are filed only after the registration statement is declared effective and carry the final or supplemental prospectus.
If the question concerns marketing and pricing of a live offering, use 424B. If it concerns substantive disclosure changes before effectiveness, use 424A.
Parent registration statements (S-1, S-3, S-4, F-1, F-3). These are the registration statements under which a 424A is filed; they are not interchangeable with 424A. S-1/F-1 are long-form registrations for domestic and foreign issuers; S-3/F-3 are short-form shelf registrations for seasoned issuers; S-4 covers business combinations. The parent forms include Part II exhibits, undertakings, and signatures; a 424A is the prospectus document only, carrying the most current prospectus text after substantive revision but before effectiveness.
Pre-effective amendments (S-1/A, S-3/A, S-4/A, F-1/A, F-3/A). The neighbor most often confused with 424A. Both reflect substantive pre-effective changes and frequently appear together around staff comment-letter responses. The difference is structural: an /A is a marked-up amendment to the full registration statement (with exhibits and signatures), filed under Rule 472 to amend the registration; a 424A is a standalone prospectus filed under Rule 424(a) for distribution to investors. For the legal record of registration changes and the comment cycle, use /A. For what investors were actually shown in the pre-effective prospectus, use 424A.
Form 497 (investment company prospectuses). The 1940 Act analog. Rule 497 governs prospectus filings for registered investment companies (mutual funds, ETFs, closed-end funds), where effectiveness mechanics under Section 8(b) and Rule 485 differ such that no direct "pre-effective substantive change" form exists. Issuer populations between 424A and 497 are essentially disjoint: operating companies file 424A, registered funds file 497 (and 497K summary prospectuses).
Free Writing Prospectuses (FWP, Rule 433). Written offering communications that fall outside the statutory prospectus. FWPs share the pre-effective marketing window with 424A but carry term sheets, roadshow materials, and supplemental marketing content rather than the statutory prospectus text. They supplement, but do not replace, the 424A. A 424A is a complete revised statutory prospectus; an FWP is a discrete communication that must be consistent with, and accompanied or preceded by, the statutory prospectus.
Form 8-A. A short Exchange Act Section 12 registration used to list a class of securities, typically alongside an IPO. It frequently appears in the same file cluster as 424A but has no disclosure overlap: 8-A documents the listing of a class of securities; 424A documents the substantive prospectus content of the offering itself.
Form 424A is the only filing in this cluster that is simultaneously (i) pre-effective, (ii) structured as a standalone prospectus rather than a registration statement or amendment, and (iii) triggered specifically by substantive changes versus a previously filed prospectus. That combination separates it from the post-effective 424B variants, from the parent S-/F- registration statements and their /A amendments, from FWPs as non-statutory communications, from Rule 497 as the investment-company channel, and from 8-A as an Exchange Act listing mechanism. The dataset is the correct primary source for tracking how an operating-company registrant's prospectus evolved during the pre-effective comment-and-revision window; it is not a substitute for the final prospectus, the registration record, or surrounding marketing communications, and is best paired with those neighbors when reconstructing a complete offering history.
Form 424A captures pre-effective amendments to a live prospectus. Each record marks a moment where an offering's disclosure changed before effectiveness, which makes the dataset useful to a narrow set of professionals working on or around securities offerings.
Securities lawyers in IPO and follow-on practice mine 424A filings for precedent on how peers disclosed mid-process changes: revised offering size, added or removed selling stockholders, restated financials, new lock-up terms, or updated litigation and regulatory disclosure. They diff risk factors, use-of-proceeds, dilution tables, and plan-of-distribution language across comparable deals to draft first amendments, respond to staff comment letters, and decide whether a change is substantive enough to require 424(a) treatment rather than a 424(b) supplement.
Bankers on equity and debt capital markets desks watch cover-page deal terms, underwriter economics, over-allotment and lock-up provisions, and plan-of-distribution wording on 424A filings to read live deal flow. When a peer issuer files a 424A, syndicate professionals assess whether the amendment shifts marketing, pricing, or timing of effectiveness, and they pull the filing into comparable-deal precedent searches and post-mortems on completed offerings.
Sell-side and buy-side analysts compare a 424A against the prior S-1 or S-3 to detect changes in the business description, segment reporting, customer concentration, MD&A, capitalization, dilution, and restated financials. New material weakness language, revised guidance, or amended use-of-proceeds drives model revisions and updated valuation ranges. Analysts also build historical panels mapping pre-effective changes to first-day pop, aftermarket volatility, and lockup-expiry performance.
In-house counsel and finance teams at registrants use prior 424A filings as a drafting library when preparing their own pre-effective amendments. Amended risk factors, capitalization and indebtedness, executive compensation, related-party transactions, and legal proceedings sections from comparable issuers calibrate disclosure choices around staff comments, new financing arrangements, or management changes mid-registration.
Compliance staff at issuers, underwriters, and broker-dealers reconcile distributed prospectus versions against the latest EDGAR-filed 424A to confirm that no roadshow material is being circulated against an outdated prospectus. They track filing timestamps, document hashes, and the substantive content of amended sections to test compliance with Rule 424(a) timing and to document internal controls over offering procedures.
Plaintiff and defense lawyers handling Section 11 and Section 12(a)(2) claims use 424A filings as primary evidence of what was disclosed and when. They diff Risk Factors between successive 424A versions and the effective 424B3 to detect last-minute disclosure changes, line up amendment timing against roadshow events, and use the resulting timeline in complaint drafting, motions to dismiss, expert reports, and enforcement investigations. The precise wording of amended risk factors, financial statements, MD&A, and related-party disclosure is the core evidence.
Empirical researchers measure textual change between S-1/S-3 filings and 424A amendments to study pre-effective drift, comment-letter influence, underpricing, and litigation incidence. Common workflows include topic-tagging amended sections, computing similarity scores against the original registration statement, and joining filing-level changes to first-day returns or subsequent class-action filings.
Quant and NLP engineers pair each 424A with its S-1/S-3 ancestor and effective 424B prospectus to train models that classify substantive changes, score disclosure novelty, and detect offering events in near real time. The HTML, TXT, and PDF document content supports section-level diffing of risk factors, use-of-proceeds, and capitalization, while CIK, accession number, and filing date metadata enable clean joins to registration, pricing, and post-IPO performance datasets.
The dataset is narrow but information-dense. Capital markets lawyers, syndicate bankers, IPO analysts, in-house disclosure teams, compliance officers, securities litigators, academic researchers, and quant/NLP teams all read different sections of the same record, anchored on one fact: a 424A documents a substantive disclosure change made before an offering went effective.
The most useful workflows pair the 424A document with its parent registration statement (S-1/S-3/S-4) or its later 424(b) post-effective prospectus to isolate exactly what changed and when.
Capital markets lawyers and sell-side analysts diff the Risk Factors, MD&A, and Use of Proceeds sections of a 424A against the most recent S-1 or S-3/A from the same fileNo (the 333- Securities Act file number on entities[]). The output is a section-level changelog showing added risks, restated financials, or revised proceeds language introduced in response to staff comments, used to draft amendments for comparable deals or to flag material disclosure shifts mid-registration.
Securities litigators handling Section 11 and 12(a)(2) claims pair the final 424A prospectus with the effective 424B1/B3/B4 filed against the same registration. Diffing cover-page terms, dilution tables, capitalization, and Risk Factors between the two reveals last-minute disclosures or omissions and produces an evidentiary timeline keyed to filedAt timestamps, suitable for complaint exhibits and expert reports.
ECM and DCM syndicate desks query the prospectus body for the Underwriting (Plan of Distribution) section, lock-up provisions, over-allotment options, and underwriter syndicate listings on 424A filings within a peer SIC group. The resulting precedent set supports pricing and structure conversations on live mandates and post-mortems on completed deals where the 424A captured the final pre-effective economics.
Credit analysts and fixed-income data teams parse entities[] across 424A records to extract parent issuer plus guarantor subsidiary or co-registrant relationships, joined on cik and fileNo. This produces a guarantor-structure dataset for registered debt offerings, used to score structural subordination and to validate guarantor coverage against indenture exhibits attached to the parent S-3 or S-4.
Quant and NLP teams build labeled triples of (parent S-1/S-3 prospectus, 424A pre-effective prospectus, 424B post-effective prospectus) joined on the 333- file number. Section-level text from the prospectus HTML body, after stripping the SGML envelope, trains models that classify whether a change is substantive enough to require 424(a) treatment versus a 424(b) supplement, and that score disclosure novelty in real time when new pre-effective filings hit EDGAR.
Offering compliance officers at issuers and underwriters hash the primary 424A document and compare it against the prospectus version circulated to investors and posted on roadshow platforms. The linkToFilingDetails URL, filedAt timestamp, and document content together support a control attesting that no marketing material was distributed against a superseded prospectus during the pre-effective window.
Dataset Index JSON API: [https://api.sec-api.io/datasets/form-424a-files.json](https://sec-api.io/datasets)
This endpoint returns the dataset's metadata and the full list of container files. The response includes the dataset name, description, last updated timestamp, earliest sample date (1994-01-01), total records, total size, covered form types (424A), container format (ZIP), and content file types (TXT, JSON, HTML, PDF). It also includes the download URL for the entire dataset archive and an array of per-container entries with each container's key, size, record count, updated timestamp, and individual download URL. This endpoint does not require an API key. Use it to monitor which monthly containers were touched in the most recent refresh run and decide which ones to re-download incrementally.
Example response:
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{
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"datasetId": "1f13365b-9ae0-698f-8830-0c0551c3657d",
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"datasetDownloadUrl": "https://api.sec-api.io/datasets/form-424a-files.zip",
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"name": "Form 424A Files Dataset",
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"description": "Form 424A filings contain prospectuses filed pursuant to Rule 424(a) under the Securities Act of 1933. These are pre-effective prospectuses that include substantive changes from or additions to a prospectus previously filed with the SEC as part of a registration statement.",
6
"updatedAt": "2026-04-15T11:56:04.398Z",
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"earliestSampleDate": "1994-01-01",
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"totalRecords": 1582,
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"totalSize": 94414597,
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"formTypes": ["424A"],
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"containerFormat": "ZIP",
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"fileTypes": ["TXT", "JSON", "HTML", "PDF"],
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"containers": [
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{
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"downloadUrl": "https://api.sec-api.io/datasets/form-424a-files/2026/2026-03.zip",
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"key": "2026/2026-03.zip",
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"size": 1854213,
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"records": 7,
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"updatedAt": "2026-04-15T11:56:04.398Z"
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}
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]
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}
Download Entire Dataset: [https://api.sec-api.io/datasets/form-424a-files.zip](https://sec-api.io/datasets)?token=YOUR_API_KEY
Downloads the complete Form 424A dataset as a single ZIP archive covering all filings from 1994 to the present. This endpoint requires an API key.
Download Single Container: [https://api.sec-api.io/datasets/form-424a-files/2026/2026-03.zip](https://sec-api.io/datasets)?token=YOUR_API_KEY
Downloads one monthly container ZIP file containing the 424A filings for that specific month. Use this pattern (/<YYYY>/<YYYY-MM>.zip) to fetch only the months you need based on the container list returned by the dataset index API. This endpoint requires an API key.
Form 424A is a prospectus filing made under Rule 424(a) of the Securities Act of 1933. It is a pre-effective preliminary prospectus that contains substantive changes from, or substantive additions to, a prospectus previously filed as part of a registration statement (typically S-1, S-3, S-4, S-11, F-1, F-3, or F-4) that has not yet been declared effective.
One record corresponds to a single EDGAR filing of Form 424A, identified by a unique SEC accession number. In the monthly ZIP containers, each record is a folder named with the 18-digit dash-stripped accession number, containing a structured metadata.json plus the original prospectus document and any non-image exhibits from the EDGAR submission.
The filer is always the issuer-registrant of the underlying Securities Act registration statement — the same legal entity that signed and submitted the parent S-1, S-3, S-4, S-11, F-1, F-3, or F-4. Underwriters, selling shareholders, and other parties named in the prospectus do not file the 424A in their own capacity, even when they drive its content.
The trigger is event-driven, not periodic. Rule 424(a) requires the filing no later than the date the substantively revised pre-effective prospectus is first sent or given to any person, while the registration statement is still pending. A single registration statement can produce multiple 424A filings as the preliminary prospectus is iterated and re-circulated before pricing.
The defining difference is timing relative to effectiveness. Form 424A is the pre-effective variant, filed before the registration statement is declared effective and reflecting substantive changes versus a previously filed prospectus. The Rule 424(b) variants (424B1 through 424B8) are post-effective filings that carry the final or supplemental prospectus once the registration statement is effective, including pricing information, shelf takedowns, and selling-shareholder updates.
Coverage begins with the earliest sample date of 1994-01-01 and runs through the present. The dataset is distributed as one ZIP container per calendar month, organized as form-424a-files/<year>/<year>-<month>.zip. Inside each container, file types include TXT, JSON, HTML/HTM, and PDF; image files (JPG, GIF) referenced by the prospectus are deliberately excluded but remain enumerated with EDGAR URLs in the metadata.
The dataset index is available at https://api.sec-api.io/datasets/form-424a-files.json and requires no API key; it lists every monthly container with download URLs, sizes, record counts, and updated timestamps. The full archive can be downloaded from https://api.sec-api.io/datasets/form-424a-files.zip?token=YOUR_API_KEY, and individual months can be fetched with the pattern https://api.sec-api.io/datasets/form-424a-files/<YYYY>/<YYYY-MM>.zip?token=YOUR_API_KEY.