About onlinefileconverter
We're building the file converter we always wished existed — fast, private, and free.
Our Mission
For years, converting a file meant uploading it to a stranger's server, waiting in a queue, and trusting that they'd actually delete it afterward. We thought that was strange. Modern browsers are powerful enough to convert images, documents, audio, and video without sending a single byte over the network — so we built a tool that does exactly that.
onlinefileconverter is our answer to bloated, ad-ridden, privacy-violating conversion websites. Every conversion runs locally in your browser using JavaScript and WebAssembly. Your files stay on your device. Always.
Our Story
onlinefileconverter started as a personal frustration. One of our team needed to convert a single HEIC photo from an iPhone into a JPG to attach to an email. The first three sites we tried asked for a sign-up, slapped a watermark on the result, or rate-limited free users to one file per hour. The fourth uploaded the photo to a server in an unknown country with no stated retention policy. For a single photo of a coffee cup, that felt absurd.
We knew the browser could do better. Chrome, Firefox, Safari, and Edge have all shipped WebAssembly, multi-threaded Web Workers, and the File System Access API. Combined, those primitives are enough to run the same encoders desktop apps use — directly inside a tab, with zero network round-trips. So we built it. The first version supported only PNG ↔ JPG. Today we cover dozens of image, audio, video, document, and archive formats, plus PDF tools, unit conversion, and compression — and we're still adding more.
What We Stand For
Privacy First
Your files are processed entirely in your browser. We never see them, store them, or transmit them to any server.
Speed Matters
No upload queues, no waiting rooms. Conversions happen instantly using your device's own processing power.
Free for Everyone
No paywalls, no hidden limits, no premium tiers. File conversion should be accessible to everyone, everywhere.
Built on Open Web
Powered by modern browser APIs, WebAssembly, and Canvas. No proprietary plugins or downloads required.
How Browser-Based Conversion Works
When you drop a file into onlinefileconverter, your browser reads it into memory using standard Web APIs like FileReader and Canvas. The conversion runs on your device — using your CPU, your RAM, your power. The output file is generated locally and offered as a download. At no point does the file (or any data derived from it) travel across the internet.
This means conversions are limited only by your own device's capabilities — and they're inherently private. Even if our servers were compromised tomorrow, there would be nothing for an attacker to steal, because we never had your files in the first place. You can verify this for yourself: open your browser's developer tools, switch to the Network tab, and run a conversion. You'll see no file upload — just the static page assets that loaded when you first arrived.
Under the Hood
The technologies that make in-browser conversion possible.
WebAssembly (WASM)
Runs heavyweight encoders like FFmpeg, libheif, and PDF engines at near-native speed inside the browser sandbox.
Canvas & OffscreenCanvas APIs
Handles image decoding, resizing, and re-encoding for formats like JPG, PNG, and WebP without leaving the page.
Web Workers
Moves CPU-intensive conversions off the main thread so the UI stays responsive even on multi-hundred-megabyte files.
File System Access & Blob APIs
Reads your dropped files into memory and offers the converted output as a download — all without a single network request.
Frequently Asked Questions
Is onlinefileconverter really free?
Yes. There are no paywalls, conversion limits, watermarks, or premium tiers. The site is supported by unobtrusive display ads, which is what keeps the tools free for everyone.
How can conversion happen without uploading my files?
Modern browsers can run sophisticated code — including video encoders, PDF parsers, and image codecs — directly on your device. We bundle those libraries (compiled to WebAssembly) into the page, so the work happens locally in the same way a desktop app would.
What's the maximum file size?
There is no fixed limit set by us. The practical ceiling is your device's available RAM and the browser's per-tab memory cap. On a modern laptop, multi-gigabyte video conversions are realistic; on older phones, anything above a few hundred MB may struggle.
Will my conversions work offline?
Once the page has loaded once, most conversions will continue to work even if your internet connection drops, because the actual conversion code is already running on your device.
Why do I see ads if everything is local?
Hosting, bandwidth, and domain costs aren't free even when conversions are. Display ads pay those bills so we don't have to charge users or introduce arbitrary file-size limits.