Everything runs directly in your browser using WebAssembly. No files are uploaded to any server — ever. What you convert or edit stays on your machine.
Edit before you convert
Crop, resize, rotate, remove backgrounds, and adjust brightness or contrast right in the browser — no extra apps needed. Try the free image editor →
Batch convert anything
Drop an entire folder of images at once. Preview each one side-by-side before saving. Edit and convert all with a few clicks.
How it works
1
Drop your files
Drag images or video onto the box, or click to browse. Batch upload a whole folder at once.
2
Edit or convert
Crop, resize, rotate and adjust your images. Or pick a format and quality level for conversion.
3
Save your files
Download one at a time or hit Save All. Your files are ready instantly.
Most file converters work the same way: you upload your file to a server, the server converts it, and you download the result. Your file sits on someone else’s machine in between, and you take it on trust that it gets deleted.
Filesmith doesn’t have that server. The conversion runs inside the page you’re already looking at, using two things every modern browser ships with.
Images use your browser’s own encoders
When you convert a photo here, the image is drawn to a canvas and handed to the encoder built into your browser — the same code Chrome or Firefox uses to save any image. There’s no library to download and nothing to wait for. It also means a file converted in Chrome and the same file converted in Firefox can come out a few kilobytes apart, because they ship different encoders.
Audio and video use FFmpeg, compiled to run in a tab
FFmpeg is the media engine behind most video software you’ve ever used. A WebAssembly build of it — about 23 MB — downloads from a CDN the first time you convert audio or video, then stays cached for later visits. That download is the engine, not your file. Your file never goes anywhere.
This is why the first video conversion is slow and the rest are fast, and why image conversion is quick from the very first file — images don’t touch FFmpeg at all.
The trade-off is honest: your device does the work. A desktop chews through a large video that a phone will refuse. There’s no queue and no server capacity to share, but there’s also no server to fall back on when your hardware runs out.
Which format should you use?
Most people arrive here knowing what they have and not what they want. This is the short version.
Sending a photo to someoneJPGOpens on everything ever made. PNG to JPG or HEIC to JPG if your phone saved it in something the recipient can’t open.
Putting a photo on a websiteAVIFSmallest by a wide margin at the same visual quality. Serve WebP as a fallback for older browsers, and keep a JPG for anything ancient.
Anything with a transparent backgroundPNG / WEBPJPG cannot store transparency at all. Convert a cut-out logo to JPG and the transparent area comes back solid white — permanently.
Screenshots, diagrams, anything with textPNGPhotographic compression smears sharp edges. Lossless WebP is usually smaller than PNG with no quality cost — one 243 KB screenshot here came out at 65 KB.
Keeping an original safePNG / TIFFLossless means editing and re-saving forever without degrading. Large, and worth it for anything you can’t re-shoot.
Music you’re just listening toMP3Plays on everything. FLAC to MP3 when a lossless library is too big for a phone.
Video that has to play anywhereMP4MKV, MOV and AVI all hold the same kind of video — MP4 is simply the box that TVs, phones and editors all agree to open.
The one rule worth remembering
Converting back to a lossless format does not restore quality. Once detail is gone it’s gone, and the lossless format just spends more space storing what’s left. An 85 KB WebP converted to PNG here became 1,009 KB — nearly twelve times bigger, pixel-for-pixel identical. A 324 KB MP3 became a 2,576 KB WAV that sounds exactly the same.
Convert backwards for compatibility when something won’t open. Never do it hoping for quality.
Where these numbers come from
Every converter page on this site quotes a real before-and-after. Not “up to 90% smaller” — an actual file, at stated settings, with the sizes printed next to each other.
The PNG to JPG page says 2,327 KB became 452 KB, and names the photo it happened to. WebP to PNG says the file got 11.8 times larger and suggests you probably don’t want to. Four converters here recommend against using them.
That’s not modesty, it’s what running the test produces when you publish the result either way. The methodology page lists the source files, the libraries, and — just as importantly — what these comparisons can’t tell you.
What Filesmith won’t do
Running in a browser tab buys privacy and costs capability. The honest list:
Very large video will fail. A tab only gets so much memory, and a phone gives up well before a desktop. Several-gigabyte files are slow at best and may not finish. Closing other tabs genuinely helps.
There’s no history. No account means nothing is stored, which also means nothing is recoverable. Close the tab and the work is gone. Save as you go.
Lossy conversions are one-way. Converting to JPG, MP3 or a compressed video discards detail permanently. Keep your original until you’re certain.
Some conversions aren’t worth doing. Where the measurement says a conversion will hurt more than help, the page says so at the top instead of quietly running it anyway.
For everything else — a few files, a format that won’t open, a photo that’s too big to email — this works, it’s free, and nothing you drop here is uploaded anywhere.
Frequently Asked
How does Filesmith keep my files private?
Your files never leave your device. Filesmith runs entirely in your browser using WebAssembly and the Canvas API — the same technology browsers use to render games and video. There's no server receiving your files. Nothing is uploaded, logged, or stored anywhere.
What's the difference between the converters and the image editor?
The converter on this page is for quickly changing file formats (JPG to WEBP, MP4 to MP3, and so on) and simple edits like cropping or resizing. The image editor is a full editing suite with layers, masks, brushes, background removal, curves, filters, and more — closer to a Photoshop alternative, also running fully in your browser.
Do I need to install anything or create an account?
No to both. Filesmith is a free web app that runs directly in your browser. There's nothing to download, no installer, no account, and no email required. Just open the page, drop your files, and go.
Which browsers does Filesmith work in?
Any modern browser with WebAssembly support: Chrome, Firefox, Safari, and Edge on both desktop and mobile. For best performance, use an up-to-date version of Chrome or Firefox. Very old browsers (pre-2018) may not support all features.
Why does the first audio or video conversion take longer?
Audio and video run on FFmpeg, and the engine itself — roughly 23 MB — downloads the first time you use one on a device. After that your browser caches it and later conversions start immediately. Image and document conversions never touch FFmpeg and are fast from the very first file.
Is there a file size limit?
Filesmith doesn’t impose one. The real limit is your device’s memory, since everything is processed locally. Images and documents are rarely a problem. Very large video — several gigabytes — may be slow or run into browser memory limits, and a phone will hit that wall sooner than a desktop. If a file fails, closing other tabs to free memory often fixes it.
Why do some pages tell me not to convert?
Because the measurement said so. Converting an already-compressed file to a lossless format makes it much larger without recovering any quality — one 85 KB WebP became a 1,009 KB PNG. Those converters still work, because sometimes you need the format regardless, but the page tells you the cost before you spend it. See the methodology page for how that’s tested.
Will the same file give the same result in every browser?
For audio, video and documents, yes — those run through pinned libraries that behave identically everywhere. For images, not quite: Filesmith uses your browser’s built-in encoder, and Chrome, Firefox and Safari each ship a different one. The same photo at the same quality setting can come out a few kilobytes apart. The figures published on this site were measured in Chrome.