Diffly — Compare Two Files Online

Compare two versions of a file online: text, code, JSON, XML, YAML, CSV, PDF, Word, Excel and images. See what was added, removed and changed. Files stay in your browser.

Beta: this tool works for common files but is still being improved; see Limitations below.

Compare Text, Code and Data Files

Drop the original file on the left and the updated one on the right. Text and source code are compared line by line with word-level highlights, in side-by-side or unified view, and unchanged runs fold away. JSON, YAML and XML are compared as structures, so you see paths like $.user.email with old and new values, and key order can be ignored. CSV rows can be matched by position or by a key column such as an ID, with each changed cell listed.

PDF, Word and Excel

PDF text is compared page by page with changed, added and removed pages listed; Visual pages compare renders the pages and highlights changed pixels for layout and image changes that text can't show. Word documents are compared paragraph by paragraph, including headings and table cells. Excel workbooks are compared cell by cell with addresses like Sheet1!B4, formulas and values reported separately, and added, removed or renamed sheets detected. Formatting, charts, macros and comments are not compared.

Images, Exports and Privacy

Images are compared pixel by pixel with a heatmap, an opacity slider and the exact count of changed pixels; when sizes differ you choose to align, scale or stop. Every result can be exported as a TXT or HTML report, JSON, CSV or a PNG difference image. Both files are read and compared in your browser and are never uploaded; Reset clears them.

Frequently asked questions

Are my files uploaded?
No. Diffly reads and compares both files in your browser. Nothing is sent to a server, and closing or resetting the page clears them.
Which file types can I compare?
Plain text and source code, Markdown, JSON, XML, YAML, CSV, PDF (text, or page images in visual mode), Word .docx, Excel .xlsx and images (PNG, JPG, WebP, BMP, GIF and SVG). A PDF can also be compared with a .txt or .md file. Old .doc and .xls files aren't supported; save them as .docx or .xlsx first.
Does PDF comparison catch every change?
Text compare finds changes in the PDF's extractable text, page by page. It can't see images, layout, fonts or annotations, so use Visual pages compare for those. Scanned PDFs have no text and need visual compare or OCR.
How does Excel comparison work?
Each cell is compared and changes are shown with addresses like Sheet1!B4. Formulas and stored values are reported separately, rows can be matched by position or by a key column, and added, removed and renamed sheets are detected. Formatting, charts and macros are not compared, and formulas are not recalculated.
How are images compared?
Pixel by pixel. You get the changed-pixel count, a heatmap and an opacity slider. A tolerant setting ignores tiny colour noise from re-saving. It is a pixel comparison, not an AI understanding of the picture.
Can I save the comparison?
Yes: export a TXT or HTML report, JSON for structured results, CSV for cell or key changes, a PNG difference image for images, or print the report.

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