What is the Repair PDF tool?
A PDF is a strict little database of objects with an index at the end of the file. Break the index, chop off the tail, or corrupt one object, and a viewer that refuses anything unexpected will simply say the file is damaged — even though most of your pages are still sitting in there. This tool lets you repair corrupted PDF online free by re-parsing what is actually present and writing a fresh, valid document around it.
The first thing it does is tell you the truth. Before any recovery runs, the file is scanned twice: once to see whether the object structure can be parsed at all, and once page by page to see how many pages a renderer can open and how many characters of text survived on each. You get a count of pages found, pages with text, a plain-language verdict, and a list of the pages that could not be read — plus a Source and Recovered preview so you can look at them before committing.
Be clear about the limit, because no tool can get around it: repair means reassembling data that is still in the file. If a download stopped at 40% or a crash truncated the file, the bytes for the missing pages never arrived, and nothing can invent them. What you can do is recover everything that did arrive, which is usually far more than the viewer's error message suggests. The whole process runs in your browser, so a corrupted file that might hold sensitive work never gets uploaded anywhere.
How to fix a damaged PDF
- Drop the file on the upload area. The scan starts by itself — no button to press.
- Read the report: pages found, pages with text, file size, and a verdict line for the object structure and for the page-by-page probe. Unreadable pages are listed underneath.
- Check the Recovery strategy chip that was picked for you — “Rebuild structure” when the objects still parse, “Re-render pages” when they do not — or choose another. The hint under the chips explains the trade-off.
- Adjust the extras if you need to: keep or drop metadata, flatten form fields, recover only certain pages, or set the DPI and JPEG quality used when pages are re-rendered.
- Compare Source and Recovered in the preview. Pages marked “not recoverable” with a red banner will be missing from the download; that is your honest expectation.
- Press Repair PDF to save the rebuilt file. The status line reports how many pages came back and which ones were skipped.
Key features
- Diagnosis before recovery — the scan reports parsed page count, how many probed pages opened, roughly how many characters of text survived, and whether the file is encrypted.
- Three recovery strategies — rebuild the cross-reference structure, re-render every page that still opens, or salvage the text layer on its own.
- A named list of the casualties — pages that cannot be read are listed and flagged in the preview, so nothing disappears from the output without telling you.
- Recovered preview, not a promise — the right-hand panel renders the actual rebuilt document for your current settings; what you scroll through is what downloads.
- Selective recovery — pull back only the pages you care about with a range such as 1-3, 7, 9-12, useful when one bad page keeps stalling a viewer.
- Metadata and form control — keep the original document info or strip it, and optionally flatten form fields so their values are baked into the page.
- Tunable re-render quality — 36 to 600 DPI and JPEG quality from 40% to 98% when pages have to be rasterised.
Benefits of using this PDF repair tool
- You find out what is salvageable in seconds. Instead of guessing why a PDF will not open, you get a page-level report and can stop worrying about the pages that are fine.
- Nothing is uploaded. Broken files are still your files — a half-corrupt tax return or thesis is repaired locally, not handed to an anonymous recovery service.
- A fallback when the clean route fails. If the structure is too damaged to rebuild, re-rendering only needs each page to open once, and text salvage only needs the words.
- No signup, no file-size gate, no watermark. Recovery services love to show you a preview and then ask for a card; here the download is just your file.
- Honest output. The status line names every skipped page, so you know exactly what you are sending on to someone else.
Who should use this tool?
Students facing a deadline
The upload portal rejects your dissertation, or Acrobat says the file is damaged an hour before it is due. Run the scan: if the structure parses, “Rebuild structure” usually produces a file that opens everywhere within seconds, with your text still selectable for the plagiarism checker.
Anyone with a half-downloaded or crash-damaged file
An interrupted download, a full disk, a USB stick pulled out mid-write or a phone that died while saving all leave the same signature: the beginning of the document is intact and the end is gone. The probe shows you how far the good data reaches, and re-rendering that range gives you a working PDF of the surviving pages.
Office and archive staff
Old network shares are full of PDFs produced by long-dead scanners and report generators that never quite followed the spec. Rebuilding them once produces files that today's viewers accept, and dropping stale metadata at the same time keeps the archive tidy.
Developers and support teams
When your own pipeline emits a PDF that one library rejects, the scan separates “the structure is broken” from “one page fails to render”, which is usually the difference between a bug in your writer and a bad font. Rebuilding also gives you a clean file to attach to the ticket.
Frequently asked questions
Can a corrupted PDF always be recovered?
No, and any tool that promises otherwise is selling something. Damage to the index, the trailer or a few objects is usually repairable because the page data is still present. Content that never made it into the file — a truncated download, an overwritten block — cannot be reconstructed by anyone.
My PDF won't open at all. Is it worth trying?
Yes, that is exactly the case this is for. The scan runs a lenient parser and a page-by-page probe, so it often opens files that a strict viewer rejects outright. If neither the structure nor a single page can be read, it tells you plainly that the file is not salvageable rather than handing you an empty PDF.
Which recovery strategy should I use?
Start with the one selected for you. “Rebuild structure” is best when it works — text, vectors, links and forms all survive. “Re-render pages” draws each readable page as an image, which almost always opens but loses selectable text. “Salvage text only” re-types the words at their original coordinates when the graphics are gone.
Why are some pages missing from the recovered file?
Because they could not be read. Those page numbers appear in the report, get a red “not recoverable” banner in the preview, and are named again in the status line after the repair. The rest of the document is still recovered around them.
Will the repaired PDF look exactly like the original?
With “Rebuild structure”, yes — the same page objects are written into a valid file. Re-rendered pages are visually the same but are now images, so zooming very far in shows pixels and the text cannot be selected. Text salvage keeps the words and their positions, not the layout, images or fonts.
Why does the report say only 400 pages were probed?
The diagnosis stops probing after 400 pages to keep the scan quick on huge documents. The recovery itself is not limited that way — it processes every page in the file, or just the range you type under Advanced options.
Can it repair a password-protected PDF?
Partly. Encrypted files are opened in a permissive mode and the report warns you, but for a complete recovery remove the password with the Unlock PDF tool first and then repair the unlocked copy.
Is my damaged file uploaded anywhere?
No. The scan, the rebuild and the download all happen in your browser tab using pdf.js and pdf-lib, so the file stays on your device. That also means you can repair confidential documents without clearing it with anyone first.
Related tools you might need
Do not delete that file yet. Drop it in above to repair corrupted PDF online free and see page by page what can still be recovered.
Scan my PDF now