FLV to MP4 is built for video editing and conversion jobs that fit cleanly into a browser tab. Rescue Flash Video (FLV) files by converting them to modern MP4 in your browser. Files are processed locally with FFmpeg WebAssembly — no uploads, no sign up, no watermarks. The processing runs in the page itself, which is why the controls update instantly when you change settings and why a freshly loaded page is ready to do real work the moment it becomes interactive.
The processing pipeline is straightforward: your input is parsed by FFmpeg compiled to WebAssembly, transformed according to the options you select, and serialised back into a downloadable result. Accepted input formats are MP4, WebM, MOV, MKV, AVI, FLV, and OGV. The 500 MB per-file ceiling matches what a typical browser tab can handle without paging to disk.
FLV to MP4 is shaped around the recurring needs of two audiences: creators trimming short clips, who use it as a quick utility between bigger tools, and students submitting video assignments, who use it as their primary way of getting the job done. Both groups get the same defaults and the same speed.
FLV to MP4 is structured so the question "where is my file processed?" has a single answer: in your browser tab. The engine, the controls, and the result panel are all on one page. Navigating away or closing the tab clears the page's memory the way it does for every other tab.
Reach for FLV to MP4 when you need a predictable result on a single file. The page works on the first visit, the controls are visible without a menu, and the output is delivered the moment the engine finishes.
Output handling is intentionally boring: FLV to MP4 produces `{name}-edited.{ext}` and triggers your browser's standard "save" behaviour. If you have a default download folder configured, that is where it will land. There is no Favtoo-side history of jobs you have run.
The 500 MB ceiling on input size is the only fixed limit. Output files are produced in standard formats that every common viewer recognises, and the tool runs the same way regardless of how many times you have used it during the session.
As a workflow component, FLV to MP4 is the part you reach for when a single, well-defined video editing and conversion step needs to happen. It performs that step and returns a standard file you can carry into the next part of your pipeline.
FLV to MP4 keeps the control set focused. Every option on the page is there because a real workflow needs it, and the defaults aim at the most common case so a first-time user can get the right output without changing any settings.
FLV to MP4 is structured around the idea that a useful tool should be its own page. Open the page, do the work, close the tab — the page is the entire product. There is no onboarding flow because there is nothing to onboard into.
FLV to MP4 fits the gap where opening a desktop app feels heavy and writing a script feels overkill. The page handles the common video editing and conversion task with sensible defaults so a single visit usually completes the job; for highly specialised work, a dedicated desktop application can offer more knobs to turn.
Pro tip: FLV to MP4 works just as well in a private/incognito window as in a normal one, which is occasionally useful when you want zero browser-history footprint of the job. Another tip: if the tool ever feels slow, it is almost always because the browser tab is competing for CPU with another tab — pausing or closing the heavy ones gives the engine room to work.
For most failure modes, refreshing the page and re-running the job is enough — the engine has no persistent state to corrupt. If the same input fails twice in a row, the input itself is most likely the problem (a truncated file, an unexpected variant of the format, or a stream the engine does not recognise).
That is essentially everything FLV to MP4 does and how it does it. Open the tool above, drop in your input, and the work happens in the page. If you find yourself reaching for it often, bookmark the page — it loads quickly on subsequent visits, and your most-recent settings are remembered for the rest of the session.
A WebAssembly build of FFmpeg loads in this page and re-encodes your FLV to MP4 using libx264 + AAC. The bytes are read into JavaScript memory, transcoded locally, and returned as a downloadable MP4 — they never touch a server.
Server-side tools use native multi-threaded FFmpeg with hardware acceleration. WebAssembly is single-threaded with no GPU encode access, so a typical FLV-to-MP4 run takes 3–8× longer than native FFmpeg. The trade-off is total privacy: your file never leaves your device.
Flash is dead — modern browsers, phones, and players cannot read FLV. Converting to MP4 future-proofs the file and makes it playable everywhere from iPhones to smart TVs to YouTube uploads.
Yes. FFmpeg WASM decodes Sorenson Spark (H.263), VP6, FLV1, and the rare H.264-in-FLV variants, then re-encodes to modern H.264 for the MP4 output.
Up to 500MB. Most FLVs are small to begin with (Flash era streams were heavily compressed), so this is rarely a problem.
Often yes — H.264 at decent quality is more verbose than the heavily-compressed VP6 or Sorenson encodes typical of old FLVs. Use the Small quality preset or run Video Compressor afterward to bring the size back down.
Nellymoser, MP3, and AAC audio inside FLVs are all decoded automatically and re-encoded to AAC 128 Kbps stereo — the standard for MP4 and supported everywhere.
No. The conversion runs entirely in your browser tab. Nothing is transmitted, stored, or logged. Closing the tab erases the file from memory immediately.
Your file is processed inside your browser by FFmpeg compiled to WebAssembly. The engine reads the file's bytes from your tab's memory, computes the result, and writes the result back into the tab. You can confirm what the page does by opening developer tools and watching the Network tab during a run — the requests you see are for the tool's static assets only.
Inputs are capped at 500 MB per file, which keeps memory usage stable across phones, tablets and older laptops. You can run FLV to MP4 as often as you need; every run produces a full-quality result.
FLV to MP4 is built to preserve quality wherever the underlying video format allows it. Operations that are mathematically lossless (e.g. structural transformations, lossless re-encoding) round-trip with no perceptible change. Operations that involve a lossy codec inevitably introduce small artefacts at the byte level, but the defaults aim at the sweet spot where output looks or sounds the same to a normal viewer or listener while still being meaningfully smaller or faster than the input.
Favtoo keeps no copy of your file because Favtoo never receives your file. FLV to MP4 runs entirely in your browser, the input is held only in your tab's memory, and closing the tab discards it. There is no opt-in cloud history, no "recent jobs" panel synced to an account, and no server-side retention to configure — the architecture simply has nowhere for your file to be stored.
Failures usually fall into one of three buckets: the input is in an unsupported format, the input is over the size cap, or the input is structurally malformed (a truncated download, a partial export, or a stream the engine does not recognise). The first two are easy to confirm — check that your file is one of MP4, WebM, MOV, MKV, AVI, FLV, and OGV and that it is below 500 MB. For the third, opening the file in its native viewer first is the fastest way to confirm the source is intact.
Desktop apps usually have more advanced features but require installation, maintenance and (often) a licence. Paid online tools are convenient but route your file through their servers and gate downloads behind accounts. FLV to MP4 sits in between: free, instant, and private, but intentionally narrow in scope. For one-off jobs and the common video editing and conversion operations, it is usually the lowest-friction choice; for highly specialised work, a dedicated app is still the right answer.
Most jobs finish in seconds. Speed scales with input size and with how many CPU cycles your browser tab has available — the engine runs in your browser, so it shares resources with whatever else you have open. For inputs near the 500 MB ceiling, expect anywhere from a few seconds to roughly a minute on a typical laptop. Closing other heavy tabs noticeably speeds things up.
No installation is needed. FLV to MP4 runs as a normal web page, with no browser extension, no native helper, and no separate desktop client to download. That is partly a privacy choice — extensions can request broad permissions, while a regular page is sandboxed by default — and partly a convenience one: you can use FLV to MP4 on any computer you have temporary access to without leaving anything installed on it.
FLV to MP4 is updated whenever the underlying engine releases an improvement or a bug fix. Because the tool is delivered as a static page, every visit fetches the latest version automatically — there is no "version" to manage on your end. If a particular release ever changes default behaviour, the change is documented on Favtoo's changelog so you can confirm what shifted.
Video to GIF
Convert any video clip to an animated GIF entirely in your browser. Pick the start, length, frame rate, and width — your file is processed locally with FFmpeg WebAssembly and never uploaded.
Screen Recorder
Record your screen, a window, or a browser tab directly in your browser. Optionally include system audio and your microphone. Capture, preview, and download the video without installing any app — and without uploading anything.
Webcam Recorder
Record your webcam directly in your browser with optional microphone audio. Pick the resolution (480p, 720p, or 1080p), frame rate, and mirror mode, then capture and download the result without installing any app.
Screen + Webcam Recorder
Record your screen with your webcam composited into a picture-in-picture corner — perfect for tutorials, course videos, demos, and reaction recordings. Pick the camera position, size, and audio sources, then capture and download in your browser.
Video Slideshow Maker
Turn a stack of photos into an MP4 slideshow with per-slide durations, crossfades, and an optional soundtrack. Pick the resolution (up to 1080p), frame rate, and transitions, then download a single MP4 — all processed in your browser with FFmpeg WebAssembly.
Video from Images + Audio
Combine a stack of photos with a music track or narration into a single MP4 video. Pick the resolution, per-slide duration, transitions, and let the slideshow length match the audio. All processed in your browser with FFmpeg WebAssembly.
Video Trimmer
Set precise in and out timestamps, snap to keyframes when needed, and document handles for social-safe cutdowns.
Video Splitter
Split any video into 2–10 equal-length pieces, packaged as a downloadable ZIP. Files are processed entirely in your browser with FFmpeg WebAssembly using lossless stream-copy.