What does converting an image format mean?
Every image file wraps the same basic thing — a grid of colored pixels — in a different container with its own rules for how that data is stored and compressed. Converting an image changes the container: a JPG becomes a PNG, a HEIC becomes a JPG, a PNG becomes a WebP. The picture you see stays the same, but the file gains or loses traits like transparency support, animation, compression efficiency, and, crucially, compatibility with the app or website you need to use it in.
Most people convert for one of three reasons: a format won't open where they need it (HEIC on Windows is the classic example), a format is too large for the web and a smaller one will do, or a destination demands a specific format (a print shop wanting TIFF, a marketplace wanting JPG, a design tool wanting PNG). This tool handles all of those by decoding your file in the browser and re-saving it in the format you pick.
Converting HEIC from an iPhone
Since iOS 11, iPhones save photos as HEIC by default. It is a genuinely good format — about half the size of JPEG at comparable quality — but it was born inside Apple's ecosystem and the rest of the world has been slow to catch up. Drop a HEIC into a Windows app, a web upload form, or an older photo editor and you will often get an error or a blank thumbnail.
Converting HEIC to JPG or PNG solves this instantly. OpusImg decodes the HEIC right in your browser using a WebAssembly build of libheif — the same open-source library behind most HEIC support elsewhere — so you do not need Apple software and the photo never leaves your device. The result is a standard JPG or PNG that opens everywhere, with no upload, no account, and no quality compromise beyond the single re-encode.
JPG, PNG, or WebP: choosing a target
JPG is the universal photo format. It has no transparency and is lossy, but it is understood by every device, app, and upload form ever made, which makes it the safe choice when you just need a photo to work somewhere. PNG is lossless and supports transparency, so it is the right pick for screenshots, logos, icons, diagrams, and any image with sharp edges or text where artifacts would be obvious.
WebP is the modern middle ground. It compresses 25–35% smaller than JPG at the same visual quality, supports transparency like PNG, and is now supported by every current browser. If your image is bound for the web and you do not need maximum legacy compatibility, converting to WebP is usually the best single decision for page speed. AVIF compresses even harder and HEIC is great inside the Apple world, but both are Pro features here; the free tool covers the three formats that handle the overwhelming majority of real conversions.
Transparency and animation
Transparency only survives a conversion if the target format supports it. PNG and WebP both carry an alpha channel, so a logo with a see-through background stays clean. Convert that same logo to JPG and the transparent areas are flattened onto a solid background, because JPG has no concept of transparency at all. The converter surfaces which targets preserve transparency so the trade-off is never a surprise.
Animation is the one area where format conversion gets genuinely hard. An animated GIF or animated WebP contains many frames plus timing data. This tool converts the first frame to a still image in your chosen format, which is exactly what most people want when they need a thumbnail or poster image. Re-encoding a full animation frame-by-frame into another animated container is a larger feature that is planned separately rather than bundled into the everyday converter.
Everything runs in your browser
Most online converters upload your images to a server, transcode them in the cloud, and send the result back. Your private photos and confidential documents pass through someone else's infrastructure, where they may be logged, cached, or retained. OpusImg works differently: conversion happens entirely on your device using WebAssembly codecs, including the libheif decoder for HEIC and pure-JavaScript decoding for TIFF.
When you drop a file, it is decoded, re-encoded in your chosen format, and handed straight back to you without a single byte being uploaded. There is no server to trust, nothing to delete afterward, and the tool keeps working even if you go offline. It is the same fast, modern conversion you would expect from a desktop app — delivered through a web page that respects your privacy by design.