How to troubleshooting the zip comment editor
- Step 1Confirm the input is really a ZIP — Comments only exist in ZIP-format files. If the editor says 'Not a valid ZIP archive', the file is a 7z/tar/rar/gzip or a corrupt ZIP. Check the real format with auto-format-detector at /archive-tools/auto-format-detector.
- Step 2If it's a damaged ZIP, repair first — A truncated ZIP whose EOCD record was lost cannot be edited — the comment can't be located. Run corrupted-zip-repair to rebuild the central directory and EOCD, then return here.
- Step 3Check the comment length — If your comment came out shorter than typed, you exceeded 65,535 bytes. The tool slices text to 65,535 characters; for multibyte text the encoded bytes can be the real limit. Shorten the comment or store long text as a file.
- Step 4Verify the file is under your tier cap — A ZIP over your tier's size limit is rejected before processing. Free is 50 MB / 500 entries; Pro 500 MB / 50,000; Pro-media and Developer 2 GB / 500,000. The whole file loads into memory, so the cap is checked up front.
- Step 5Remember it replaces, not appends — If your previous comment 'disappeared', that's expected — typing a new comment overwrites the old one. Read the current text with comment-extractor first if you need to keep part of it.
- Step 6Confirm the result — After editing, check the result metrics (
Comment length,Removed?) and verify withunzip -zor comment-extractor. The download is named<name>-with-comment.zip.
Symptom to cause to fix
The handful of issues that account for nearly all comment-editor problems.
| Symptom | Real cause | Fix |
|---|---|---|
| 'Not a valid ZIP archive — no EOCD' | Input has no EOCD (7z/tar/rar/gzip, or corrupt ZIP) | Detect format with auto-format-detector; repair with corrupted-zip-repair; or convert with archive-format-converter |
| Comment came out truncated | Exceeded the 65,535-byte ZIP cap | Shorten the comment; store long text as a file in the archive |
| Old comment is gone | Tool replaces, doesn't append | Read old text with comment-extractor, retype combined |
| File rejected before processing | Over tier size/entry cap | Use a higher tier or a smaller archive |
| Can't see the current comment | This tool only writes | Use comment-extractor to read it |
| Edited a .docx and it 'broke' | Renamed wrong, or relied on trailing junk | Rename output back to .docx; don't edit files with meaningful post-EOCD data |
Error-vs-expected outcomes
Which conditions are genuine errors and which are intended behaviour.
| Condition | Outcome | Is it a bug? |
|---|---|---|
| Non-ZIP input | Error: not a valid ZIP | No — comments are ZIP-only |
| Empty textarea | Comment removed (length 0) | No — that's how you remove it |
| Comment > 65,535 bytes | Sliced to fit | No — ZIP format limit |
| Existing comment overwritten | Replaced by new text | No — replace is by design |
| Bytes after EOCD overwritten | Treated as comment, replaced | No — but avoid on files with meaningful trailing data |
| File over tier cap | Rejected | No — limit enforced up front |
Tier limits (per archive)
Real limits for the archive family; the comment editor takes one file at a time.
| Tier | Max file size | Max entries | Files at once |
|---|---|---|---|
| Free | 50 MB | 500 | 1 |
| Pro | 500 MB | 50,000 | 20 |
| Pro-media | 2 GB | 500,000 | 100 |
| Developer | 2 GB | 500,000 | unlimited |
Cookbook
Each common failure with the exact diagnosis and the corrective action.
'Not a valid ZIP archive' on a .7z
The most frequent error. The file is a 7z (or tar/rar/gzip), which has no EOCD record, so the comment cannot be located.
Input: backup.7z
Error: Not a valid ZIP archive — no End of Central
Directory record found.
Diagnosis: 7z has no global comment.
Fix: convert to ZIP with archive-format-converter,
then add the comment here.Comment shorter than you typed
You pasted a long block and the result was cut off. The ZIP comment field caps at 65,535 bytes.
Typed: 80,000-character changelog
Result metric: Comment length: 65535
Diagnosis: sliced to the 65,535-byte cap.
Fix: keep the comment short; store the full changelog
as CHANGELOG.txt inside the archive instead.'My old comment vanished'
You typed a new note and the previous comment is gone. The tool replaces the entire comment — it does not append.
Old comment: Release notes v1
Typed: Patch applied
Result: Patch applied (old text overwritten)
Fix: read the old comment first with comment-extractor,
then retype both together — there is no append mode.File rejected before anything happens
A large archive is refused immediately. The size cap is enforced before the edit because the whole file is read into memory.
Input: release.zip (180 MB), tier: Free (50 MB cap) Result: rejected before processing Fix: upgrade tier (Pro = 500 MB) or reduce the archive.
Can't see the current comment to confirm a change
This tool only writes. To read the comment before or after editing, use the reader sibling.
To read: comment-extractor (/archive-tools/comment-extractor) or CLI: unzip -z archive.zip To write/remove: this tool (zip-comment-editor)
Edge cases and what actually happens
Input is 7z, tar, rar, or gzip
ErrorThese have no End of Central Directory record, so the tool throws 'Not a valid ZIP archive'. Comments are ZIP-specific. Identify the format with auto-format-detector and convert to ZIP with archive-format-converter if you need a comment.
Corrupt ZIP with a missing EOCD
ErrorIf the PK\x05\x06 signature isn't in the last 65,557 bytes, the comment can't be found and the edit fails. Rebuild the directory with corrupted-zip-repair first.
Comment exceeds 65,535 bytes
TruncatedThe ZIP comment-length field is 2 bytes (max 65,535). The tool slices longer text to 65,535 characters before encoding. Store long text inside the archive as a file instead.
Multibyte comment near the limit
Length caveatThe slice is by character count, so a sub-65,535-character comment with many multibyte characters can encode to more than 65,535 bytes — beyond the 2-byte length field. Keep non-ASCII comments well under the limit.
Expecting the old comment to be kept
ReplacedThe tool overwrites the whole comment. There is no append mode. To extend an existing comment, read it with comment-extractor and retype the combined text.
Empty textarea on a file with no comment
By designThe output is effectively identical to the input (comment length stays 0) and Removed? reports true. This is a harmless no-op, not an error.
File has meaningful data after the EOCD
OverwrittenEverything after the 22-byte EOCD header is treated as the comment and overwritten. Self-extracting stubs are before the data, so they're safe, but appended hidden data after the EOCD would be lost — don't edit such files here.
Browser extension blocks scripts
BlockedIf a privacy/script-blocking extension prevents the page's JavaScript from running, the edit won't execute. The processing is local JS, not WASM-heavy for this tool, so allow scripts for the page or try a clean browser profile.
File over the tier size or entry cap
RejectedA ZIP larger than your tier's size cap, or with more entries than the tier allows, is rejected before processing. Free is 50 MB / 500 entries; higher tiers go up to 2 GB / 500,000 entries.
Frequently asked questions
Why do I get 'Not a valid ZIP archive'?
The file has no End of Central Directory record. That means it's a non-ZIP format (7z, tar, rar, gzip) or a corrupt ZIP whose EOCD was lost. Comments are ZIP-only. Detect the format with auto-format-detector, repair a damaged ZIP with corrupted-zip-repair, or convert with archive-format-converter.
Why is my comment shorter than what I typed?
It exceeded the ZIP comment cap of 65,535 bytes. The tool slices longer text to 65,535 characters before encoding. For long text, store it as a file inside the archive instead of in the comment.
Where did my existing comment go?
The tool replaces the whole comment — it does not append. Whatever you type becomes the entire new comment. To keep the old text, read it first with comment-extractor and retype it together with your addition.
Why was my file rejected immediately?
It exceeded your tier's size or entry limit. Free allows 50 MB and 500 entries; Pro 500 MB and 50,000; Pro-media and Developer 2 GB and 500,000. The whole file is loaded into memory, so the cap is enforced before processing.
How do I actually remove a comment?
Leave the textarea empty and run the edit. The comment-length field is set to 0, the comment is removed, and the result metric Removed? shows true.
Why can't I see the current comment?
This tool only writes a new comment. To read an existing one, use comment-extractor at /archive-tools/comment-extractor, or run unzip -z archive.zip on the command line.
I edited a .docx and now it won't open — why?
Most likely you didn't rename the download. The output is <name>-with-comment.zip; rename it back to .docx. If the document still fails, the file may have relied on data after the EOCD, which this tool overwrites — don't edit such files here.
Does editing the comment ever corrupt the entries?
No. The tool preserves the central directory and all compressed entries byte-for-byte and rewrites only the trailing comment and its length field. The file list and contents are unchanged.
It seems stuck on a large file — what's happening?
The whole file is read into memory once for the edit, so a very large ZIP near your tier cap can take a moment. If it's beyond the cap it will be rejected outright rather than hang. Reduce the file or use a higher tier.
Can emoji or accented characters cause problems?
They're supported via UTF-8, but they're multibyte. Because the length slice is by character count, a comment full of multibyte characters can encode to more than 65,535 bytes. Keep non-ASCII comments well under the limit.
Why does the whole-file hash change after editing?
Because the trailing comment and the 2-byte length field changed. The entries themselves are byte-identical, so extracted-file hashes are unchanged; only the whole-file hash moves by the comment delta.
What's the difference between this and the metadata or signing tools?
This edits the EOCD comment only. To read full header metadata use archive-metadata-extractor, to read an existing comment use comment-extractor, and to inspect signature blocks use archive-signing-info — all at /archive-tools/<tool-id>.
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.