A Convertio Alternative That Converts Files Locally
Convertio's whole pitch is breadth: throw almost any file format at it and it'll convert it to almost any other. That breadth comes from running the actual conversion work on Convertio's own servers, which means every file you convert, whatever it is, gets uploaded there first. For a random test file that's nothing to think twice about. For a video from a client shoot, a spreadsheet of customer data, or a scanned document, it's a real question worth asking: does this file actually need to leave my computer just to change its format?
Often, it doesn't. Modern browsers can do a lot of what used to require a server: decode and re-encode images, run real video/audio codecs through WebAssembly builds of FFmpeg, parse and rewrite data formats like CSV, JSON, and XML. DuckConvert is built entirely on that idea.
Format coverage, without the upload
DuckConvert converts across the same broad categories Convertio is known for, all processed locally:
- Image Converter — PNG, JPG, WebP, AVIF, HEIC, SVG, BMP, TIFF, and more, converted between each other.
- Video & Audio Converter — MP4, MOV, WebM, MKV, MP3, WAV, and others, powered by FFmpeg compiled to WebAssembly.
- Data & Docs Converter — CSV, JSON, YAML, XML, DOCX, XLSX, and HTML, converted between formats developers and analysts actually work with.
- Geodata Converter — KML and GPX to GeoJSON, for mapping and GIS work.
- PDF Tools — merge, split, and convert PDFs to and from images.
How conversion works without a server round-trip
Each category uses whatever the browser can do natively or via WebAssembly: the Canvas API and native decoders for images, a WebAssembly build of FFmpeg for video and audio, and pure JavaScript parsers for data formats. None of it depends on sending your file anywhere — the conversion runs on your own device's CPU, in memory, for as long as the tab is open.
You don't have to trust that description blindly. Open your browser's DevTools Network tab before converting a file and watch that nothing carrying its contents goes out over the network. The How It Works page shows exactly what to check for.
Convertio vs. DuckConvert
| | Convertio | DuckConvert | |---|---|---| | Where files are processed | Their servers | Your browser, locally | | Free tier limits | File size and daily conversion caps | None — bounded only by your device | | Account required | No, but limits are stricter without one | No | | Format coverage | Very broad (300+ formats) | Broad, focused on commonly-needed pairs |
Frequently Asked Questions
Does DuckConvert support as many formats as Convertio? Not quite as many — Convertio's catalog runs into the hundreds of niche formats. DuckConvert focuses on the formats people actually convert day to day: common image, video, audio, and data formats, plus PDF workflows. See the full list on the supported formats page.
Is conversion quality the same as a server-based tool? Yes, generally — DuckConvert uses the same underlying technology (real codecs, real parsers) that server-side tools use, just running in your browser's WebAssembly runtime instead of on a remote machine.
Why is video/audio conversion sometimes slower than image conversion? Video and audio codecs are computationally heavier than image encoding, and your device's CPU is doing the work instead of a server farm's. For most everyday clips this still finishes in well under a minute; very large files take proportionally longer.
Do I need to install anything? No. Everything runs in the browser tab you're already in — no browser extension, no desktop app, no account.
If your files don't need to travel further than your own browser tab, there's no real reason to hand them to a server. Try converting your next file locally instead.