browser-native · privacy-first · MIT
Convert any file in your browser,
without ever uploading it.
Optimal Convertis a privacy-first file converter that runs every transform directly in the user’s browser using WebAssembly. PDFs, images, audio, and video are processed client-side — throughput is bounded by your hardware, not a shared render fleet, and files are never uploaded.
- Zero server uploads
- Works fully offline
- GDPR · HIPAA safe by default
local conversion ledger
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↳ actually running · 0 bytes have crossed the wire
what to convert
PDFs, images, audio, and video — in any direction
The converter engine understands formats the way your files actually change hands: a client sends one type, your workflow needs another. You’ll find a pair for the common swaps and the awkward ones alike.
Documents & PDFs
- Build a PDF from images
- Export a PDF to a page format you can edit, or flatten it back to a pixel image for sharing without a reader.
Image formats
- JPG to WebP — the biggest win for page weight
- PNG to JPG, and back the other way when you need a lossless cutout.
- HEIC to JPG for iPhone photos that refuse to open elsewhere.
- Everything PNG, JPG, WebP, HEIC, AVIF, and SVG: see the image converter hub.
Audio formats
- Deliver lossless FLAC or WAV and shrink to a widely-playable MP3 or M4A without re-encoding artefacts where you don’t need them. Start at the audio converter hub.
Video formats
- Re-wrap clips between MP4, WebM, and MOV for the player that needs them, all in-browser. Head to the video converter hub.
why it matters
No upload means your files never leave your device
Most online converters work by shipping your document to a render fleet and handing back a finished file. That means you are trusting a stranger’s server with whatever is inside — a patient record, a draft contract, a cut of a video. Optimal Convert inverts the model: the WebAssembly engine and every format module run inside your own tab.
Practically, that buys three things. Privacy by default — no upload endpoint exists, so there is nothing to intercept, log, or leak. Unlimited size — because your hardware does the work, throughput is bounded by your device, not a shared quota. And offline use — once the engine is loaded, the conversion keeps running even if you drop offline mid-task.
This is why the project publishes the engine as open source and releases the format modules under an MIT license: if your clinic, law firm, or compliance team needs to audit exactly what runs on their machines, they can. Head to the how-it-runs page for the technical walkthrough.
what the engine converts
One drop, every format the engine knows
The browser engine handles raster images (JPG, PNG, WebP, HEIC, AVIF, GIF, BMP, TIFF, ICO), PDF pages, audio (MP3, WAV, FLAC, OGG, M4A, AAC) and video (MP4, MOV, MKV, AVI to WebM or an animated GIF). You drop a file once and can export it to any supported target in the same session — each result downloads separately.
Because the conversion runs on your own hardware, there is no queue, no per-file price, and no size cap beyond what your device and browser can hold in memory. The small, versioned Wasm modules load on demand and are cached after the first visit, so repeat conversions keep working offline. Nothing about the workflow needs an account, a sign-up, or a server at the other end.
pick the right format
Plain-English format guides
Converters handle the how. The harder question is the which— and that’s what the guides answer, honestly, without hype.
JPG vs PNG
When compression’s worthwhile and when it bites.
PNG vs WebP
The modern image format, demystified with real numbers.
What is WebP?
Why every site asks for it and when to say yes.
MP3 vs WAV
Lossy vs lossless audio, in plain terms.
2026 format benchmarks
Original measurements, not vendor claims.
Browse all guides
The full plain-English library.
get started
Your next conversion is already free.
No accounts. No rate limits. No watermarks. Every conversion runs in your browser. If you’re a clinic, law firm, or regulated team that needs to audit the pipeline, write to us — we’ll point you at the engine source and the format modules.