Most online converters send your files to a cloud server the moment you click convert. Convertlo does the opposite — every conversion runs inside your browser using WebAssembly and the HTML5 Canvas API. Your files are processed by your own CPU, never transmitted anywhere, and are deleted from memory when you close the tab. Supports 190+ formats across images, documents, audio, and video — all without a single byte leaving your device.
Files never travel over the network, so they cannot be intercepted, logged, or retained by a third-party server. What never leaves your machine cannot be breached.
After the first page load, all tools work without an internet connection. Convert confidential files on an air-gapped machine or a restricted corporate network with no issues.
No data leaves your browser, so there is no data processor relationship to manage. No DPA required, no privacy policy concerns about file storage, no retention schedules to negotiate.
No upload means no waiting for a server to receive, queue, and process your file. Conversion starts immediately and runs at the full speed of your device's CPU and GPU.
| File Type | Convertlo | CloudConvert | TinyPNG | Convertio |
|---|---|---|---|---|
| JPG / PNG / WebP / AVIF | ✓ Browser | ✗ Uploads | ✗ Uploads | ✗ Uploads |
| HEIC / GIF / BMP / SVG | ✓ Browser | ✗ Uploads | ✗ Uploads | ✗ Uploads |
| PDF documents | ✓ Browser | ✗ Uploads | ✗ N/A | ✗ Uploads |
| MP3 / WAV / FLAC audio | ✓ Browser | ✗ Uploads | ✗ N/A | ✗ Uploads |
| MP4 / WebM / MOV video | ✓ Browser | ✗ Uploads | ✗ N/A | ✗ Uploads |
| Daily limit | Unlimited | 25/day | ~20/day | 10/day |
| Account required | Never | Optional | Never | Optional |
No backend magic — just your browser running real conversion algorithms via WebAssembly. Here is exactly what happens when you convert a file on Convertlo.
Your file is read into memory by the browser's FileReader API. This is a sandboxed operation: the file data is available only to the current page's JavaScript context. Nothing leaves your device at this stage or any stage after.
WebAssembly modules handle the heavy lifting: FFmpeg.wasm for video and audio transcoding, the Canvas API and libvips-style pipelines for image format conversion, and pdf.js for PDF rendering and extraction. These are the same algorithms used on servers, running on your own machine instead.
The converted output is written directly to your device via the browser's download API — a temporary object URL generated from an in-memory blob. No server receives the file at any point. Closing the tab clears all file data from memory.
No. All conversion in Convertlo uses browser APIs — the Canvas API for images, FFmpeg.wasm for video and audio, and pdf.js for documents. Files are decoded entirely in memory on your device, and nothing is transmitted over the network at any point. After the first page load, the tools even work fully offline.
A browser-based image converter is software that runs entirely inside your web browser using JavaScript and WebAssembly — no server processing is needed. Your files are processed by your own CPU or GPU inside the browser's sandboxed environment, giving you the same level of privacy as local desktop software but with no installation required.
Yes. Browser-based converters offer the same privacy as offline desktop software. Files are processed inside the browser's sandboxed environment and are never accessible to the website's servers because they are never transmitted to them. This makes Convertlo appropriate for legal briefs, HR records, medical images, and sensitive corporate documents.
After the first page load, yes. Convertlo uses a service worker to cache the tool assets locally on your device. Return visits work without an internet connection — your conversions run entirely on your hardware whether you are online or offline. This also makes it usable on restricted or air-gapped networks.
Convertlo converts JPG/JPEG, PNG, WebP, AVIF, HEIC, GIF, BMP, SVG, and TIFF images without uploading anything. It also handles PDF documents, MP3/WAV/FLAC/AAC audio, and MP4/WebM/MOV video — all browser-based, all zero upload, across 190+ format combinations.
The practical limit is your device's available RAM, not a server-imposed cap. Convertlo recommends keeping images and documents under 50 MB for smooth, reliable performance. Video and audio files can often be larger depending on how much memory your device has free at the time of conversion.
Server-side processing is simpler to build and allows conversion of formats the browser cannot handle natively. The tradeoff is that your files travel to their servers. Browser-based conversion is technically harder to build — it requires WebAssembly for formats like WebP and a full port of FFmpeg for video and audio — but it gives users complete file privacy with no data ever leaving their device.
190+ formats. Images, documents, audio, video. Your files never leave your browser.
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