Error Level Analysis (ELA)
Error level analysis re-saves the image as a JPEG at a fixed quality and shows how much each area changed, brightened so the differences can be seen. Areas saved the same number of times tend to change by similar amounts, so a pasted or retouched region can stand out. It is a heuristic for directing a closer look, not proof of editing: edges, textures, text, resizing and re-saving all make untouched photos uneven too.
- Processed locally
- No upload, no wait
- No sign-up
- No watermark
Drop images here
or choose files · paste with Ctrl/⌘ V
JPG, PNG, WebP, HEIC, AVIF, GIF, TIFF, SVG, RAW, PSD, JXL, BMP, ICO and more
How to use Error Level Analysis
- 1
Drop your images, choose files, or paste from the clipboard.
- 2
Adjust the options. The preview updates as you change them.
- 3
Click Analyse. Files are processed on your device.
- 4
Download each result or everything as a ZIP.
Why use Aback Images for error level analysis
Adjustable comparison
Choose the re-save quality and how strongly the differences are amplified, and see the result update live.
Lossless result
The analysis image is saved as PNG, so the error pattern is not disturbed by a second compression.
Honest about limits
ELA highlights compression differences, which edits can cause and so can ordinary edges, text and re-saving.
Processed on your device
Your images are decoded, edited and encoded inside this browser tab by Web Workers. Nothing is uploaded to a server.
About Error Level Analysis
How error level analysis works
JPEG compression discards information in 8×8 pixel blocks. Re-saving at a fixed quality changes each block by an amount that depends on how often and how strongly it was compressed before. Measuring and brightening that change shows which areas have a different compression history from the rest of the picture.
Because textures, sharp edges, text and colour saturation also change the error level, ELA output always needs interpretation, ideally alongside metadata checks and other evidence.
Limitations
- Error level analysis is a heuristic. Bright regions are not proof of manipulation and dark regions are not proof of authenticity.
- Results are most meaningful for JPEGs that have not been resized or re-compressed by social networks or messaging apps.
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Frequently asked questions
Does a bright area mean the photo was edited?
No. Sharp edges, fine texture, text and saturated colours always show higher error levels, and an untouched photo that was resized or re-saved can look uneven. Compare similar surfaces, such as two patches of sky, rather than reading brightness on its own, and treat any finding as a reason to look for other evidence.
Which images give useful results?
JPEGs close to their first save. Screenshots, PNGs and images re-compressed many times, for example by social networks, give little contrast, because every area has already settled at a similar error level.
Are my images uploaded anywhere?
No. Processing happens inside your browser with WebAssembly and Web Workers. The site only downloads the app code and codecs; your files never leave your device. You can confirm this with the live upload counter on the tool, or in your browser's network panel.
Can I process many files at once?
Yes. Drop a whole selection or folder. Files are processed in parallel on several worker threads, each result can be downloaded on its own, and everything can be saved as one ZIP.
Is it free? Is there a file limit or watermark?
It is free with no account, no watermark and no daily limit. The only limit is your device's memory: very large images (over roughly 100 megapixels) may be refused to keep the tab from crashing.