Home › Image Tools › Image Diff Checker
Image Diff Checker
Drop two versions of an image to see exactly what changed. Changed pixels are highlighted, boxes mark each changed area, and you get the percentage of pixels that differ. Switch to a difference map, a swipe slider or a fade to inspect the details.
0%pixels changed
0changed pixels
0changed areas
0%mean difference
0%max difference
Detection
Ignore color changes smaller than this. 0% = exact match.
Highlight view
Difference view
Advertisement
Advertisement
How to use the Image Diff Checker
- Add image A and image B: drop, paste or choose the original on the left and the changed version on the right.
- Read the result: the panel shows the % of pixels that differ and how many separate areas changed; boxes mark them on the image.
- Set the tolerance: raise it to ignore compression noise in JPG screenshots, lower it to 0 to catch every single changed value.
- Inspect: switch to Difference for a heat-style map, or Slider and Fade to flip between the two versions.
- Download diff PNG to attach the highlighted result to a bug report or review.
How the comparison works
Both images are drawn onto canvases of the same size (image A's size, or a proportionally reduced size for very large images above about 16 megapixels). For every pixel position the tool computes the difference in each channel and keeps the largest one:
Δ = max(|RA − RB|, |GA − GB|, |BA − BB|, |αA − αB|), a value from 0 to 255.
- A pixel is changed when Δ is greater than the tolerance (tolerance % × 255).
- Pixels changed = changed pixels ÷ (width × height) × 100.
- Mean difference = average Δ over all pixels ÷ 255 × 100; max difference = largest Δ ÷ 255 × 100.
- Changed areas are found by grouping changed pixels into small grid cells and merging neighbouring cells, so a changed word or button counts as one area.
Which view to use
| View | What you see | Good for |
|---|---|---|
| Highlight | Changed pixels in a bright color over a faded grayscale copy of A, with boxes | Spotting every change at a glance, bug reports |
| Difference | |A − B| per channel, amplified; black means identical | Subtle changes in color, compression artefacts, shifted edges |
| Slider | A on the left, B on the right of a draggable line | Checking alignment and layout shifts |
| Fade | B blended over A with adjustable opacity | Seeing movement, like the classic onion-skin view |
Tips for accurate results
- Compare lossless PNG files when possible. Every JPG save adds small changes that show up as noise.
- Capture both screenshots at the same zoom level, window size and device pixel ratio; a 1 px shift makes every edge look changed.
- If one image is a resized copy of the other, use Scale B to A; resampling also creates small differences, so raise the tolerance to about 10%.
Frequently asked questions
How is the percentage difference calculated?
Each pixel of image A is compared with the pixel at the same position in image B. A pixel counts as changed when the largest difference in its red, green, blue or alpha value is above the tolerance. The percentage is changed pixels ÷ total pixels × 100. The mean difference is the average of that largest channel difference over all pixels, expressed as a percentage of 255.
What tolerance should I use?
Use 0 for lossless PNG screenshots when you need to catch every change. For JPG files or screenshots that went through compression, 5 to 15% hides the noise while still finding real changes. Raise it further to find only strong changes, such as moved or replaced objects.
Can I compare images of different sizes?
Yes. Scale B to A resizes the second image to the first image's dimensions, which is right for the same picture exported at a different size. Align top-left keeps both at their original scale and compares the overlapping area, which suits screenshots where something was added at the bottom or right; uncovered areas count as changed.
Why do two identical-looking JPGs show differences?
JPEG compression changes pixel values slightly every time an image is saved, especially around edges and in smooth gradients. These differences are invisible to the eye but real. Increase the tolerance until only meaningful changes remain.
Is this useful for visual regression testing?
Yes. Compare a screenshot of a page before and after a code change to spot unintended layout or color changes. The changed-area boxes point at each region, and the diff PNG is easy to attach to a pull request or ticket.
Are my images uploaded?
No. Both images are decoded and compared with the Canvas API inside your browser. Nothing is sent to a server, so confidential screenshots stay on your device.
Related tools
Text CompareFind the differences between two texts.Before and After Image MakerCombine two photos into a labeled before and after image or an animated slider video.Image Metadata ViewerSee a photo's EXIF data: camera, lens, exposure, date and GPS location, then strip it in one click.Image Color PickerPick any pixel colour from an image and get HEX, RGB, HSL plus a paletteBackground RemoverRemove image backgrounds automatically with AI.Make Image TransparentRemove a white or solid-color background and save a transparent PNG, right in your browser.Image to Text (OCR)Extract text from images, screenshots and photos with OCR in 25+ languages, right in your browser.Image CompressorShrink images to a target size like 100 KB.Image ResizerResize images to any size without losing quality.Compress Image to 20KBShrink any photo to under 20KB (or any target size).Compress Image to 100KBShrink any photo to under 100KB automatically, with the best quality that fits.Compress JPEG to 50KBShrink photos to under 50KB for forms, passports and exams.HEIC to JPGConvert iPhone HEIC photos to JPG.WEBP to JPGConvert WEBP images to JPG in bulk.PNG to JPGBatch convert PNG images to JPG with a background color.JPG to PNGBatch convert JPG images to PNG.Image CropperCrop images, including circle crops for profile pictures.Rotate & Flip ImageRotate images by any angle or mirror them, one or many at once.Meme GeneratorMake memes with classic templates and custom text.Collage MakerCombine photos into a grid collage.Add Watermark to PhotoAdd a text or logo watermark to one or many photos at once.Blur Image & Face Pixelate ToolBlur or pixelate faces, plates and backgrounds in a photo.Pixelate Image & Pixel Art ConverterTurn any picture into pixel art with retro palettes and dithering.Logo MakerDesign a text logo with fonts, icons and colors, then save SVG or PNG.Certificate MakerDesign certificates from templates and export one or many as PDF.WEBP to PNGConvert WEBP images to PNG, keeping transparency.SVG to PNGConvert SVG graphics to PNG or JPEG at any scale.PNG to ICOCreate multi-size favicon .ico files from PNG.GIF MakerTurn videos and images into GIFs, trim and compress.Business Card MakerDesign business cards and download a print-ready PDF.Flyer MakerDesign printable and social media flyers from free templates.Poster MakerDesign posters in A0–A5 and US sizes and download a print-ready PDF.Invitation Card MakerCreate printable birthday, wedding and party invitations for free.Color Palette GeneratorGenerate beautiful color palettes and export them.HEX to RGBConvert HEX colors to RGB and other formats.RGB to HEXConvert RGB to HEX with sliders, live swatch and one-click copy.HEX to HSLConvert HEX colors to HSL and back with interactive sliders.RGB to CMYK ConverterConvert RGB and HEX colors to CMYK for print, and back.Color Contrast CheckerCheck WCAG contrast ratios and find accessible text colors.Pantone to HEXLook up approximate HEX, RGB and CMYK values for Pantone colors.Color Name FinderFind the closest color name for any HEX or RGB color.AVIF to JPGConvert AVIF images to widely supported JPG.PNG & JPG to WEBPConvert PNG and JPG images to smaller WEBP files.Aspect Ratio CalculatorCalculate image sizes for 16:9, 4:3 and any ratio.Thumbnail Safe ZonePreview YouTube and TikTok thumbnail safe zones.Color Blindness SimulatorSee any image as people with protanopia, deuteranopia, tritanopia or achromatopsia see itAdd Text to ImageAdd styled text layers with outline and shadow to any photo, then downloadThumbnail MakerDesign 1280×720 YouTube thumbnails with templates, bold text and stickersImage Border AdderAdd a border, rounded corners, matte and shadow to a photo onlineWallpaper GeneratorCreate gradient and pattern wallpapers sized for any phone, tablet or desktopColor Shades GeneratorTurn one HEX color into a 50-950 scale plus tints, shades and tones, ready to export.Round Corners ImageGive any picture rounded, circle or squircle corners and save a transparent PNG.Printable Calendar MakerMake a printable month or year calendar with holidays, then print or save PDF.YouTube Thumbnail GrabberPaste a YouTube link to get every thumbnail size, from HD 1280x720 down to 120x90.Tailwind Color GeneratorTurn one color into a full Tailwind 50–950 shade scale and export the config or CSS.Image Flipper & MirrorMirror photos horizontally or flip them vertically, one image or a whole batch.Printable Planner GeneratorDesign daily or weekly planner pages with your dates and colors, then print them as a PDF.CSS Gradient GeneratorDesign linear, radial and conic CSS gradients with draggable stops and export CSS or PNG.Grayscale Image ConverterTurn color photos into black and white with luma, luminance or average methods and sepia.Graph Paper GeneratorMake printable square, dot, isometric or hex graph paper and download it as PDF, PNG or SVG.Color MixerMix two colors in sRGB, linear, OKLab or OKLCH, or blend them with Photoshop-style modes.Photo FiltersApply 27 one-click photo filters like Vintage, Noir and Teal & Orange with an intensity slider.Lined Paper GeneratorCreate printable lined paper: wide, college or handwriting ruling, Cornell notes, PDF or PNG.Random Color GeneratorGenerate random HEX colors one at a time or in batches, with hue, saturation and lightness ranges.Photo EditorEdit photos online: brightness, contrast, saturation, crop, rotate, flip and filters with undo.Chart MakerMake bar, line, area, pie and doughnut charts from a simple table and download PNG or SVG.Color WheelFind complementary, triadic, analogous and other color harmonies on an interactive wheel.Image SharpenerSharpen soft or slightly blurry photos with a real unsharp mask and before/after view.Venn Diagram MakerMake 2- or 3-circle Venn diagrams from lists; overlaps are found for you. Export PNG or SVG.Invert Image ColorsTurn any picture into a color negative, with R/G/B channel toggles and an intensity slider.Mind Map MakerBuild mind maps fast with keyboard shortcuts and auto layout, then export PNG, SVG or JSON.Image SplitterSplit an image into a rows × columns grid of tiles and download them one by one or as a ZIP.Org Chart MakerType an indented list of names and titles and get a clean org chart to download as PNG or SVG.Image CombinerCombine images side by side, stacked or in a grid, with spacing, background color and alignment.Timeline MakerCreate horizontal or vertical timelines from dated events with colors, then save PNG or SVG.Screenshot BeautifierPut screenshots on gradient backgrounds with padding, rounded corners, shadow and a browser frame.Gantt Chart MakerPlan tasks with dates, progress and dependencies on a Gantt chart, then export PNG or CSV.Image UpscalerEnlarge images 2×, 3× or 4× with Lanczos-3 or bicubic resampling and optional sharpening.Word Cloud GeneratorTurn any text into a word cloud in shapes like a heart or star, then save it as PNG or SVG.Pie Chart MakerMake pie and donut charts with labels, percentages and a legend, then download PNG or SVG.Favicon GeneratorMake a favicon.ico, PNG icons, apple-touch-icon and web manifest from an image, text or emoji.Color PickerPick any color and get HEX, RGB, HSL, HSV and CMYK codes, shades and a screen eyedropper.HTML Color CodesAll 140 HTML color names with HEX and RGB codes, plus the 216 web-safe colors. Click to copy.Passport Photo MakerMake passport and visa photos for any country and print them on a 4x6 sheet.PNG to SVG ConverterConvert PNG or JPG images to scalable SVG vectors with color and detail control.EXIF RemoverRemove EXIF, GPS location and other metadata from JPG, PNG and WEBP photos.Image DPI ChangerChange the DPI of JPG and PNG images without re-encoding, and see the print size.Online PaintDraw and paint in your browser: brushes, shapes, fill bucket, text, undo and PNG export.Signature MakerDraw or type your signature and download it as a transparent PNG or SVG.Color Palette from ImageExtract the main colors of any photo as HEX codes, CSS variables and a palette PNG.Photo to SketchTurn any photo into a pencil, charcoal or color sketch in your browser and download it.Image ConverterConvert images between JPG, PNG, WEBP, AVIF, BMP, GIF and ICO in batches, right in your browser.HEIC to PNGConvert iPhone HEIC and HEIF photos to lossless PNG in batches, with ZIP download.GIF Frame ExtractorSplit an animated GIF into PNG frames with delays, a sprite sheet and ZIP download.GIF to MP4Convert animated GIFs to MP4 video with loops, scaling and background color, in your browser.ICO to PNGExtract every size from ICO and CUR icon files and save them as PNG images or a ZIP.Pixel Art MakerDraw pixel art on an 8 to 64 px grid with palettes, fill and mirror, then export PNG or SVG.Quote Image MakerTurn a quote into a shareable image for Instagram, Stories or X with backgrounds and fonts.Social Media Image ResizerResize photos for Instagram, Facebook, X, LinkedIn, YouTube, TikTok and Pinterest in one go.Profile Picture MakerMake a round or square profile picture with a ring border and color or gradient background.Photo Frame MakerPut photos in polaroid, film strip, gallery, rounded or shadow frames with a caption.Device Mockup GeneratorPut a screenshot into a phone, tablet, laptop, monitor or browser frame and download a PNG.Replace Color in ImageClick a color in a picture and swap it for a new color or transparency, keeping the shading.Duotone GeneratorTurn any photo into a bold two-color duotone image with presets, custom colors and intensity.Glitch Image EffectAdd RGB split, scanlines, slice shifts and noise to a photo for a digital glitch look.Emoji to ImageTurn any emoji into a PNG image from 64 to 1024 px, transparent or on a color, in batch.Text to ImageTurn text into a PNG image with your font, size, colors, padding, alignment and wrapping.Seamless Pattern GeneratorMake seamless dot, stripe, wave, grid, zigzag and check patterns. Export CSS, SVG or PNG.SVG OptimizerMinify SVG files: strip metadata, comments and editor junk, round numbers, compare sizes.Compress Image to 200KBShrink any photo to under 200KB automatically, with the best quality that fits.CMYK to RGBConvert CMYK percentages to RGB and HEX color codes with sliders and a live preview.HSL to HEXConvert HSL and HSLA colors to HEX and RGB with sliders and a live preview.HEX to RGBAConvert HEX color codes to CSS rgba() with an opacity slider and one-click copy.RGBA to HEXConvert rgba() colors to 8-digit HEX, or flatten transparency onto any background.HEX to CMYKConvert HEX color codes to CMYK percentages for print, with a live preview.