Straighten skewed scans in one click
Drop a scanned PDF and every page is measured inside your browser. Tilted pages are detected and rotated back automatically — pages that are already level pass through untouched, so their text stays selectable.
- 100% local · nothing uploaded
- Auto angle detection ±15°
- Straight pages untouched
- No sign-up
Detected skew
Your straightened PDF is ready
Fixed entirely in your browser. Open the Network panel in your browser's developer tools while using this tool — no file ever leaves your device.
Three Steps, No Upload
The whole process runs on your own machine using the browser's PDF renderer and canvas. Nothing is sent anywhere, and the tool keeps working after the page has loaded even if you go offline.
Drop your PDF
Any password-free PDF works. Multi-page scanned documents are handled page by page, so mixed feeds with different tilts come out uniformly level.
Angles measured locally
Each page is rendered and analysed with a projection-profile algorithm — the same technique professional scanning suites use — measuring tilt to a tenth of a degree.
Download the fixed copy
Tilted pages are rotated level and rebuilt at scan-grade resolution. Straight pages are copied byte-for-byte, preserving selectable text and original quality.
Where Crooked Pages Come From
Skew is the most common defect in scanned documents. These are the situations we built this tool for.
Feeder scans
Automatic document feeders pull sheets slightly askew, so multi-page contracts arrive with every page tilted a degree or two.
Old photocopies
Legacy scans were placed on the glass by hand. One pass here makes an archived batch presentable again.
Photographed receipts
Desk photos are rarely square. Straighten them before attaching to an expense claim so OCR reads them cleanly.
Notes & assignments
Handwritten pages photographed for a class portal read better — and grade better — when the lines run level.
Other Well-Known Ways to Straighten a PDF
We're not the only option, and honesty beats a hard sell. These established tools can also fix skewed PDFs — the difference is where your file goes while they do it. Cloud services upload your document to their servers; this tool never sends it anywhere.
Sejda — Deskew PDF
A dedicated deskew tool from one of the longest-running online PDF suites. Runs in the browser tab but processes files on its servers, with a daily free-task limit.
sejda.com ↗PDF24 — Straighten PDF
Free, generous and famously reliable, from the German team behind the PDF24 desktop suite. Also server-based, with a Windows desktop version if you prefer local processing.
tools.pdf24.org ↗iLovePDF & Smallpdf
The two best-known all-in-one PDF suites. Neither offers a dedicated one-click deskew, but both can rotate pages manually and repair problem files — as cloud services with free tiers.
ilovepdf.com ↗Stirling PDF
The open-source, self-hostable PDF toolkit popular with developers. If you're comfortable running Docker, it gives you server-side batch processing on hardware you control.
stirlingpdf.com ↗Frequently Asked Questions
Everything people usually ask before trusting a file tool.
How does the tool detect the angle?
Each page is rendered to an image and binarised — text becomes black, background white. The tool then projects the ink onto candidate baselines at angles from −15° to +15° and picks the angle where text lines align most sharply, a classic projection-profile method. The winning angle is refined to a tenth of a degree before the page is rotated back.
Will my text stay selectable?
Pages detected as straight are copied into the new PDF without any conversion, so their text remains fully selectable and searchable. Only pages that are actually tilted are converted to images — that's the unavoidable cost of rotating content that has no other representation.
Does fixing reduce quality?
Corrected pages are re-rendered at roughly 200 DPI and saved as high-quality JPEG. For typical scans this is visually lossless. Pages that were already straight are copied byte-for-byte with zero quality change.
Is my file uploaded anywhere?
No. The tool is a single page that runs pdf.js and pdf-lib inside your browser. There is no server, no API call and no analytics on your file. Verify it yourself: open your browser's developer tools, watch the Network tab and process a file — nothing is sent.
What tilt range can it correct?
Anything between −15° and +15° per page, which covers virtually every real-world scan. Feeder skew is typically 0.5–3°; hand-placed scans rarely exceed 10°. Tilts beyond 15° need cropping rather than deskew.
Can it fix perspective or curvature?
No — this tool performs pure rotation deskew. Perspective distortion (a page photographed at an angle) and book-curl warping need geometric unwarping, a different class of algorithm. Rotation is what most "crooked scan" complaints actually are.
How is this different from cloud deskew services?
Functionally the result is similar. The difference is privacy and cost: cloud tools upload your document to their servers to process it, and free tiers usually cap daily usage. This tool processes everything locally, so it has no usage cap and nothing to leak — relevant for contracts, medical records or anything under an NDA.
Does it work on password-protected PDFs?
No. If a PDF requires a password to open, the browser cannot render it and the tool will tell you. Remove the protection first (with the password), then straighten it here.
Related Tools
Pairs well with the rest of the PDF bench. All of them run locally, like this one.