Repair PDF
Repair Corrupted PDF Free Online – PDF Repair Tool
Fix corrupted or damaged PDFs by re-serializing and rebuilding internal structure
- Runs in your browser
- Nothing uploaded
- No sign-up
- Free, no daily limits
- 1Add your file
- 2Choose settings
- 3Download
Drop a PDF here
Choose a fileUpload a PDF to attempt repair · up to 100 MB · nothing is uploaded
100% Private: All processing happens in your browser. Your files never leave your device.
Your file is safe
It is processed inside this browser tab and never uploaded, and it is gone when you close the page.
Good to know
- Repair rebuilds the PDF from every page it can read.
- Encrypted PDFs need unlocking first.
- The Producer field is set to TryDocsy PDF Repair.
Last updated
Repair PDF diagnoses and reconstructs damaged, unreadable, or syntactically invalid PDF files directly in your web browser. When older scanning software, budget virtual printers, or interrupted transfers produce files that crash strict viewers, TryDocsy uses @cantoo/pdf-lib to parse available document objects, rebuild corrupted cross-reference (xref) tables, re-serialize page trees, and compile a clean new document.
The repair engine attempts standard parsing first. If that encounters syntax errors, it automatically falls back to lenient recovery mode with metadata updating disabled. If the internal structure is recoverable, all readable pages are migrated into a fresh container. If the stream is irreparably truncated, the client reports the exact failure condition rather than delivering an unreadable file.
How it works
1. Select the damaged PDF
Drag and drop the problematic file into the upload dropzone or click to browse. The tool accepts files up to 100 MB directly into browser memory.
2. Click Repair PDF
The parser executes PDFDocument.load(bytes, { ignoreEncryption: true }). If an exception occurs, it re-attempts parsing with updateMetadata: false to bypass malformed catalog dictionaries.
3. Inspect the repair report
Review the outcome status card. If repair succeeded, the report displays recovered page counts, metadata, and verified structural corrections (Re-serialized all page objects, Rebuilt cross-reference table, Validated page tree structure).
4. Download the repaired PDF
Click Download Repaired PDF to save the clean document. The file is saved with the -repaired suffix (for files ending in lowercase .pdf).
When you'd use it
Fixing files that trigger viewer syntax errors
Documents generated by older multi-function copiers or third-party PDF generators frequently contain malformed xref offsets, causing modern browsers to display 'Failed to load PDF document'.
Resolving blank or freezing pages in previewers
If a document opens its first two pages but crashes when navigating deeper, re-serializing the page tree resolves dangling internal object references.
Cleaning document structures before merging
Downstream utilities like Merge PDF require strictly conforming object hierarchies. Repairing legacy files beforehand prevents batch processing errors.
Standardising corrupted trailers after email transit
Email filters and security gateways sometimes append trailing characters or alter EOF markers, breaking file verification. Repair strips corrupted trailers and generates fresh EOF markers.
What repair can and cannot fix: Code limits and real error strings
PDF repair is not forensic file recreation: it operates strictly within what pdf-lib's parsing engine can understand. It is vital to understand the technical boundary between structural errors and missing data:
- **What can be fixed:** Broken cross-reference tables, incorrect byte offsets, damaged trailer dictionaries, missing root catalog pointers, and minor syntax corruption in object headers. The tool re-serializes every page via PDFDocument.create() and copyPages(), writing an entirely clean xref table.
- **What cannot be fixed:** If the file download was aborted midway and page stream bytes are missing, the tool cannot invent missing data. When both standard and lenient loading fail, RepairPDFClient surfaces the exact error: 'PDF is severely corrupted and cannot be recovered.'
- **Password-encrypted files:** If the file is locked with user password encryption and has zero readable pages, the client halts with: 'This PDF is encrypted or has no readable pages - unlock it first.' Decrypt the file with Unlock PDF before attempting repair.
Metadata handling and producer stamping
During successful reconstruction, TryDocsy transfers the existing Title, Author, and Subject properties if they were successfully parsed from the original document Info dictionary. If those fields are absent, the report notes 'Missing metadata (title, author)' as an informational finding.
To ensure transparency regarding document lineage, the tool sets the Producer property of the repaired file to 'TryDocsy PDF Repair'. If you need to restore or edit custom author or title information afterwards, use Edit PDF Metadata.
Preserving text and vector quality
Unlike crude repair tools that screenshot pages or convert them to low-resolution images, TryDocsy extracts and copies original PDF page objects natively. Vector fonts, line art, color profiles, and embedded JPEG/PNG photos remain completely uncompressed and bit-for-bit identical to the source document.
Frequently asked questions
How do I fix a corrupted PDF that won't open?
Select your corrupted file in TryDocsy Repair PDF and click Repair PDF. The tool reads available internal objects in your browser, rebuilds the cross-reference table, and exports a fresh, valid PDF that opens reliably across all viewers.
Can a damaged PDF be repaired if the file download was interrupted?
No. If a download was interrupted, the file is physically missing end-of-file byte streams and page data. Because the tool cannot fabricate missing page content, it displays the message: 'PDF is severely corrupted and cannot be recovered.' In such cases, re-download the source file from its original source.
Does this tool unlock password-protected PDFs?
No. If an encrypted PDF has unreadable pages, the tool halts with the message: 'This PDF is encrypted or has no readable pages - unlock it first.' Use /pdf/unlock to remove the password before repairing.
Will repairing a PDF make text blurry or lose quality?
No. TryDocsy does not rasterise pages to images. It copies the original vector text streams, fonts, and graphics into a new PDF document, maintaining 100% original visual fidelity.
What does the 'Actions Taken' list indicate?
The Actions Taken panel confirms that the file was rebuilt: all page objects were re-serialized, a fresh cross-reference table was generated, and the page tree structure was validated against PDF 1.7 standards.
Is my corrupted file uploaded to an online server?
No. All repair algorithms run locally inside your browser tab using WebAssembly and client-side JavaScript. Your file never leaves your computer.