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Pretty-print, minify, or validate JSON files - in your browser.
JSON
Validate mode checks if the JSON is valid without modifying it. Invalid files are reported with error details.
Yes. Choose between 2 spaces, 4 spaces, or tabs for indentation.
Free for up to 3 files per batch - upgrade for unlimited.
Your files never leave your device. All processing happens locally in your browser - no analytics, no tracking scripts, no data collection.
No waiting for uploads or downloads. Files are processed directly on your machine at native speed.
Images, PDFs, CSV, JSON, text, and GPX - 65 tools for resizing, converting, merging, plotting, and more.
Works in any modern browser. No software to download, no plugins, no sign-up. Install as a PWA for offline use.
Drag and drop files or click to browse. FileWelder automatically detects file types.
Choose from tools matched to your files. Configure options to get exactly what you need.
Save processed files individually or as a ZIP. No sign-up, no email required.
Batch-resize, compress, and convert hundreds of images for web galleries.
Format JSON, convert between CSV and JSON, and generate file listings.
Convert GPX tracks to CSV or GeoJSON, merge multi-day routes, and strip metadata.
Merge and split PDFs, add page numbers and watermarks, de-duplicate files.
Unlike online converters, FileWelder never uploads your files. No account needed, no watermarks on output, no per-file limits, no tracking scripts. Everything runs in your browser - your data stays yours.
FileWelder processes files using your browser's memory. Very large files (500 MB+) may be slow or fail on devices with limited RAM.
Yes. All 65 tools are free for up to 3 files per batch with no limits.
No. All processing happens locally in your browser.
Images, PDFs, CSV, JSON, plain text, and GPX files.
Yes. Install as a PWA for offline use.
No artificial limit. Bound by browser memory.
FileWelder processes everything locally.