How to troubleshooting the corrupted zip repair tool
- Step 1Confirm you are on Pro or higher — If you see an upgrade overlay instead of a dropzone, the tool is locked: its minimum tier is Pro. Free accounts cannot run it.
- Step 2Check the file is under your size cap — Pro caps each job at 500 MB; Pro-Media and Developer at 2 GB. A larger file throws a tier-limit error before scanning starts.
- Step 3Verify the input is really a ZIP — If you get "No recoverable local file headers found," run /archive-tools/auto-format-detector. A renamed RAR or 7z has no ZIP headers and will always fail here.
- Step 4Read the recovery report — A rate below 100% is not a bug. Subtract Recovered from Attempts — the difference is entries that were encrypted, truncated, or compressed with an unsupported method.
- Step 5Rule out browser memory — Very large files near 2 GB can exhaust tab memory since the whole file is held in RAM. Close other tabs or use a CLI that streams from disk for huge archives.
- Step 6Verify the output — If the repaired ZIP behaves oddly, run /archive-tools/archive-integrity-tester on it to confirm per-entry CRCs pass.
Error and outcome reference
Every message and result mapped to the cause in the repairZip handler and the client gating.
| Message / outcome | Cause | Fix |
|---|---|---|
| Upgrade overlay (no dropzone) | Account below the Pro minimum tier | Upgrade to Pro or higher |
| "...exceeds the {tier} tier per-job limit..." | File larger than your size cap | Upgrade tier or use a streaming CLI |
| "No recoverable local file headers found..." | No PK\x03\x04 headers — not a ZIP | Run Auto Format Detector; route to the right tool |
| Recovery rate below 100% | Some entries encrypted / truncated / unsupported method | Expected — check what was skipped |
| Some files missing from output | Encrypted, size-deferred, or directory entries skipped | Use Encrypted Archive Detector / Archive Diff to confirm |
| Tab freezes on a huge file | Whole file held in RAM near the 2 GB cap | Close tabs or use a CLI for multi-GB files |
Why entries get skipped
The exact conditions in the scan that exclude an entry from recovery.
| Condition in the scan | Result | Counts as attempt? |
|---|---|---|
| Encryption flag (bit 0) set | Skipped | Yes |
| compressedSize is 0 in the local header (streamed) | Skipped | Yes |
| data runs past end-of-file | Skipped | Yes |
| inflate throws (corrupt compressed data) | Skipped | Yes |
| name ends with / (directory marker) | Omitted | Yes |
| stored or deflate, intact, non-encrypted | Recovered | Yes |
Cookbook
Walk each symptom to its root cause using the recovery report and a quick format check.
Diagnose a no-headers error
The tool says it found nothing. Confirm whether the file is even a ZIP.
Symptom: "No recoverable local file headers found —
the file may not be a ZIP at all."
Step 1: /archive-tools/auto-format-detector
-> reports: 7-Zip (magic 37 7A BC AF)
Conclusion: not a ZIP. Use the right extractor; repair can't help.Explain a partial recovery
The report shows 80% recovered. Work out what the missing 20% was.
Report: Attempts 50 / Recovered 40 / 80% Missing 10 entries. Check encryption first: /archive-tools/encrypted-archive-detector -> 10 entries flagged encrypted -> that's the gap. The tool skips encrypted entries (no password field).
Resolve a tier-limit error
A 900 MB file is rejected on Pro before scanning.
Error: "File \"big.zip\" exceeds the pro tier per-job
limit (500 MB). Upgrade for larger files."
Fix: upgrade to Pro-Media / Developer (2 GB cap),
or run zip -FF on the file from a terminal.Verify a suspicious repaired output
The repaired ZIP opens but you want to confirm it is sound.
After repair -> data-repaired.zip Run: /archive-tools/archive-integrity-tester -> all 213 entries: CRC OK The repaired archive is structurally sound.
Handle a frozen tab on a giant file
A near-2 GB archive makes the tab unresponsive during the scan.
Cause: whole file held in RAM during the byte-scan.
Fix: close other tabs to free memory and retry,
or run zip -FF / 7z on the file (streams from disk).
The browser scan is RAM-bound, not designed for multi-GB files.Edge cases and what actually happens
Free account
Locked: Pro requiredThe tool's minimum tier is Pro. Free accounts see an upgrade overlay, not the dropzone — there is no free path to this specific tool.
No headers found
Error: no headersZero PK\x03\x04 headers means the file is not a ZIP (often a renamed RAR/7z/TAR). The tool throws "No recoverable local file headers found — the file may not be a ZIP at all." Confirm with Auto Format Detector.
Partial recovery rate
ExpectedA rate below 100% is normal when entries are encrypted, truncated, or use an unsupported compression method. It is reported, not an error — the difference between Attempts and Recovered is the skipped set.
Over the size cap
Error: tier limitFiles past 500 MB (Pro) or 2 GB (Pro-Media / Developer) throw a tier-limit error before scanning. Upgrade or use a streaming CLI.
Encrypted entries missing
Skipped by designEncrypted entries are skipped because the tool has no password input. They still count as attempts, which is why the recovery rate drops. Confirm with Encrypted Archive Detector.
Streamed entries missing
SkippedEntries written with compressedSize 0 in the local header (data-descriptor / streamed) are skipped — recovery needs a non-zero compressed size in the header.
No 30-second timeout
By designThere is no built-in processing timeout in the client. A long-running scan on a large file is the file size, not a hang — let it finish or reduce the file size.
Tab unresponsive on huge files
Memory boundThe whole file is read into RAM for the scan, so near-2 GB files can freeze a low-memory tab. Free memory or use a CLI for multi-GB archives.
Output differs from original byte-for-byte
By designThe repaired ZIP is rebuilt with fflate (deflate 6) in byte-scan order, so its bytes differ even when contents match. Compare extracted contents, not raw ZIP bytes.
Frequently asked questions
Why do I see an upgrade overlay instead of the tool?
The Corrupted ZIP Repair tool's minimum tier is Pro. Free accounts cannot run it and see an upgrade prompt. Upgrade to Pro or higher to unlock the dropzone.
Why does it say no recoverable headers were found?
The scan found no PK\x03\x04 local file headers, which means the file is not a ZIP — most often a renamed RAR, 7z, TAR, or gzip. Run Auto Format Detector to see the real format.
Why did it recover fewer files than the archive contained?
Entries that are encrypted, truncated past end-of-file, written as size-deferred streams, or compressed with an unsupported method are skipped. The recovery rate reflects only what could be decompressed.
Is a recovery rate below 100% a failure?
No. It is reported information. Subtract Recovered from Attempts to see how many entries were skipped, then check encryption with Encrypted Archive Detector or missing files with Archive Diff.
Why does it stay on Processing for a long time?
There is no timeout — a long scan reflects a large file being read into memory and walked byte-by-byte. It is not stuck; let it finish, or use a smaller file or a CLI for multi-GB archives.
Why was my file rejected before processing?
It is over your tier's size cap (500 MB on Pro, 2 GB on Pro-Media / Developer). The size check runs before the scan and throws a tier-limit error. Upgrade or use a CLI.
Why are my encrypted files not in the output?
The tool skips entries with the encryption flag set because it has no password field. Those entries need credentials and a tool that supports them; identify them with Encrypted Archive Detector.
Why does the repaired ZIP differ from the original byte-for-byte?
It is rebuilt fresh with fflate at deflate level 6 and lists entries in byte-scan order. Extracted contents are identical; only the container bytes and order differ.
Can extensions or ad blockers break it?
The scan runs locally with fflate and needs no network during processing, so blockers rarely interfere. If the page itself won't load its code, hard-refresh (Ctrl+Shift+R) or try a clean profile.
Why does the tab freeze on a very large file?
The whole file is held in RAM during the scan. Near the 2 GB cap on a low-memory device the tab can freeze. Close other tabs to free memory, or use a streaming CLI.
Can it repair a 7z or RAR file?
No. The scan only recognizes ZIP local headers. Those formats return the no-headers error. Use Auto Format Detector to identify them and route to the correct tool.
How do I verify the repaired file is actually good?
Run Archive Integrity Tester on the output to confirm per-entry CRCs pass, and Archive Metadata Extractor or File Listing Generator to inspect what was recovered.
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.