How to archive comment extractor online for free
- Step 1Open the tool — Visit /archive-tools/comment-extractor. No account is required — this tool runs on the free tier.
- Step 2Drop your ZIP archive — Drag a
.ziponto the dropzone (or click to browse). One file at a time on the free tier. The comment lives in the ZIP EOCD record, so non-ZIP formats (7z, rar, tar, gz) will simply report no comment. - Step 3Let the tool locate the EOCD — The processor reads the file into memory, then scans backwards through the last 65,557 bytes for the EOCD signature. Because the comment-length field is 16-bit, the EOCD can be no further than that from the end.
- Step 4Read the decoded comment — The 16-bit comment length is read at EOCD offset +20, and the comment bytes are decoded as UTF-8 (non-fatal — invalid bytes become the replacement character). The result panel shows the comment text plus metrics:
Comment lengthandHas comment. - Step 5Download or copy the .txt — Click Download to save
<archive>-comment.txt. The output is plain text — exactly the comment string, or(this archive has no global comment)when there is none. - Step 6Act on what you found — Use the comment for build provenance or audit. To change it, use the ZIP Comment Editor; for per-entry comments rather than the global one, use the Archive Metadata Extractor.
Where the comment lives in a ZIP
The global comment is stored once, at the end of the file, inside the EOCD record. These are the exact bytes the tool reads.
| Field | EOCD offset | Size | What the tool does |
|---|---|---|---|
| EOCD signature | +0 | 4 bytes | Scanned backwards from end of file; value 0x06054b50 (PK\x05\x06) |
| Comment length | +20 | 2 bytes (uint16, little-endian) | Read directly; max value 65535 — comments cannot exceed 65,535 bytes in standard ZIP |
| Comment bytes | +22 | 0–65,535 bytes | Decoded as UTF-8 (non-fatal); this is the text you get back |
| No EOCD found | n/a | n/a | Returns empty → output becomes (this archive has no global comment) |
What you get back
The Comment Extractor always produces a plain-text result — never JSON or CSV.
| Property | Value |
|---|---|
| Output type | txt (plain text) |
| MIME type | text/plain |
| Filename | <archive-stem>-comment.txt (e.g. release.zip → release-comment.txt) |
| Content when present | The exact UTF-8-decoded comment string |
| Content when absent | (this archive has no global comment) |
| Metrics shown | Comment length (bytes/chars) and Has comment (true/false) |
Tier limits (archive family)
Comment Extractor is free-tier. Limits below are the per-archive file size, per-archive entry count, and files-per-batch for each plan.
| Tier | Max file size | Max entries | Files per run |
|---|---|---|---|
| Free | 50 MB | 500 | 1 |
| Pro | 500 MB | 50,000 | 20 |
| Pro-Media | 2 GB | 500,000 | 100 |
| Developer | 2 GB | 500,000 | Unlimited |
| Enterprise | Unlimited | Unlimited | Unlimited |
Cookbook
Real EOCD comments you will encounter in the wild, and exactly what the tool returns for each. The output is always the plain comment string (or the no-comment notice).
A CI build stamp
Many CI pipelines write a build ID and timestamp into the ZIP comment so the artifact is self-describing. Drop the artifact in, read the stamp, no checkout needed.
Input: build-artifact.zip (has EOCD comment) Output file: build-artifact-comment.txt -------------------------------------------- build=4821 branch=main commit=9f3c1ab built=2026-06-10T14:22Z -------------------------------------------- Metrics: Comment length 56 Has comment true
A Maven-built JAR (which is a ZIP)
A .jar is a ZIP under the hood, so the same EOCD comment field applies. Maven sometimes records a build note here. Rename to .zip is not even required — drop the .jar if your browser lets you.
Input: app-1.4.0.jar (ZIP container) Output file: app-1.4.0-comment.txt -------------------------------------------- Maven build 2026-05-31 by jenkins-node-07 -------------------------------------------- Metrics: Comment length 38 Has comment true
A plain ZIP with no comment
Most archives from Explorer, Finder, or a quick zip -r have no EOCD comment. The tool says so explicitly rather than returning a blank file.
Input: photos.zip (no comment) Output file: photos-comment.txt -------------------------------------------- (this archive has no global comment) -------------------------------------------- Metrics: Comment length 0 Has comment false
A non-ZIP archive (7z)
The EOCD record is a ZIP-only structure. A 7z, rar, tar, or gz file has no EOCD, so the backward scan finds no signature and the tool reports no comment. This is expected behaviour, not an error.
Input: backup.7z (not a ZIP) Output file: backup-comment.txt -------------------------------------------- (this archive has no global comment) -------------------------------------------- Metrics: Comment length 0 Has comment false
A signing / provenance note
Some release pipelines drop a short signing or provenance string in the comment. Read it here, then verify the actual signature details with the Archive Signing Info tool.
Input: release-signed.zip Output file: release-signed-comment.txt -------------------------------------------- signed-by=release-bot key=ED25519:7c1f... 2026-06-09 -------------------------------------------- Next step: /archive-tools/archive-signing-info for signature checks
Edge cases and what actually happens
Archive has no comment
By designIf the EOCD comment-length field is 0 (or no EOCD is found), the tool returns (this archive has no global comment). Has comment reads false and Comment length is 0. This is the most common result — the vast majority of ZIPs carry no global comment.
File is not a ZIP (7z, rar, tar, gz)
ExpectedThe global comment is a ZIP EOCD feature. Non-ZIP formats have no EOCD signature, so the backward scan finds nothing and the tool reports no comment. To read metadata from those formats, use the Archive Metadata Extractor instead.
Comment longer than 65,535 bytes
Truncated by specThe EOCD comment-length field is 16-bit, capping the comment at 65,535 bytes in standard ZIP. The tool reads exactly what the length field says. Real-world comments are a few hundred bytes at most, so this limit is almost never hit.
Comment contains non-UTF-8 bytes
Preserved (lossy)Decoding uses a non-fatal UTF-8 decoder. Bytes that are not valid UTF-8 become the Unicode replacement character (U+FFFD) rather than throwing. If you see �, the original comment was written in a non-UTF-8 encoding (e.g. CP437 or Shift-JIS); the raw text was preserved up to that decode limitation.
File over the tier size limit
RejectedFree tier caps input at 50 MB per file. A larger archive is rejected before processing. Because the EOCD is near the end of the file, the size limit is about loading the file into browser memory, not about the comment itself. Pro raises the cap to 500 MB; Pro-Media and Developer to 2 GB.
ZIP64 archive
Supported (32-bit EOCD)The tool reads the standard 32-bit EOCD record, which ZIP64 archives still write for backward compatibility, including the comment field. The comment is read from there as normal.
Corrupt or truncated archive with damaged tail
May read emptyIf the EOCD record is overwritten or the file is truncated past the EOCD, the backward scan may not find the signature and the tool returns no comment. If you suspect corruption rather than a genuinely empty comment, run the Corrupted ZIP Repair tool first.
Per-entry file comments expected
Out of scopeThis tool reads only the single global archive comment. Each central-directory entry can carry its own optional comment; those are not returned here. Use the Archive Metadata Extractor for per-entry details.
Trailing data appended after the ZIP
Usually fineSelf-extracting or signed bundles sometimes append data after the EOCD. The backward scan still finds the EOCD signature within the last 65,557 bytes in most cases, so the comment reads correctly. Very large appended tails could push the EOCD out of the scan window.
Frequently asked questions
Does the Comment Extractor upload my file?
No. The archive is read with the browser File API and processed in the tab — its bytes never reach a server. Open DevTools, Network tab, during processing and you will see no outbound request carrying the file.
What output format do I get?
A plain-text file named <archive>-comment.txt with MIME type text/plain. It contains exactly the comment string, or (this archive has no global comment) if there is none. It is not JSON or CSV.
Why does it say my archive has no comment?
Either the ZIP genuinely has no global comment (the EOCD comment-length field is 0 — true for most archives), or the file is not a ZIP at all. The EOCD comment is a ZIP-only feature, so 7z, rar, tar, and gz files always report no comment.
Can it read comments from 7z or RAR files?
No. The global comment is stored in the ZIP End of Central Directory record, which 7z and RAR do not have. For metadata from those formats, use the Archive Metadata Extractor.
What's the maximum file size?
Free: 50 MB. Pro: 500 MB. Pro-Media: 2 GB. Developer: 2 GB. Enterprise: unlimited. The limit is about loading the archive into browser memory; the comment itself is tiny.
How long can a ZIP comment be?
Up to 65,535 bytes, because the EOCD comment-length field is 16-bit. Real comments are typically a few hundred bytes — a build ID, version string, or short note.
What do ZIP comments usually contain?
Build IDs, version strings, developer notes, build timestamps (Maven), plugin metadata (some IDEs), or signing/provenance strings. They are a handy place to make an artifact self-describing.
Will the comment text show special characters correctly?
The tool decodes the comment as UTF-8. If the writer used UTF-8 (most do), accents and emoji round-trip correctly. If it was written in a legacy encoding like CP437, some bytes may show as the replacement character (U+FFFD).
Do I need an account?
No. Comment Extractor is a free-tier tool. You can use it without signing up. Upgrading only raises the file-size and batch limits, which this tool barely needs since it reads one small record.
Which browsers work?
Any modern browser with WebAssembly and the File API — Chrome, Edge, Firefox, Safari, Brave, Opera, on desktop or mobile. The work this tool does is light, so even older devices handle it easily.
How do I change or remove the comment I just read?
Use the ZIP Comment Editor at /archive-tools/zip-comment-editor. It writes a new EOCD comment (or removes it with an empty string), preserving the rest of the archive.
Can I batch many archives at once?
The free tier processes one file per run. Pro allows up to 20 files per run, Pro-Media up to 100, and Developer is unlimited. For bulk archive analysis across many files, the Batch Compression Report tool accepts many archives at once.
Privacy first
Every JAD Archive tool runs entirely in your browser using fflate, @zip.js/zip.js, and the libarchive WASM bridge. Your archives never leave your device — verified by zero outbound network requests during processing.