FLV to SWF Converter

FLV vs SWF — Which One Do You Actually Need?

Both are Flash formats and both are obsolete, but they are obsolete in very different ways, and that difference decides whether this conversion makes sense for you. An .flv is plain audio and video: the delivery platform is gone, but VLC, mpv and FFmpeg still open the file today. An .swf is a Flash program — vector art, timeline, ActionScript, optionally an embedded video stream — and it needs a Flash Player runtime that Adobe shut down on 31 December 2020 and started actively blocking on 12 January 2021. So converting FLV to SWF takes a file that works and produces one that mostly does not. Do it only when a legacy Flash authoring or playback pipeline requires .swf as its input format; if you want something watchable, convert FLV to MP4 instead.

Side by Side: FLV and SWF

When to Pick SWF

• An Adobe Animate project imports video on its timeline and publishes to .swf, and the asset has to be in that format going in.
• A pre-2020 kiosk, museum installation or digital-signage player runs SWF content through a bundled projector binary and cannot be changed.
• A Flash-based e-learning package of the Articulate or Captivate era still ingests .swf assets as course media.
• You are reconstructing or preserving an archive where .swf is the required deliverable and playback is handled by an emulator.

When to Stay with FLV or Go to MP4

• You want to watch the clip. FLV already opens in VLC, mpv and FFmpeg; SWF does not, so converting makes it strictly harder to play.
• You want to share it, upload it, or put it on a phone or TV. That is what FLV to MP4 exists for — H.264 in MP4 plays essentially everywhere.
• You want to edit it. Media editors import FLV; opening an SWF means Flash authoring software.
• You care about file size. FLV1 is a 2000s-era codec, so a re-encode into it is usually larger than the H.264 many later FLV files already carry.
• You inherited an old Flash asset and want it back as ordinary video — that is the reverse trip, SWF to MP4.

How to Convert FLV to SWF

1. Upload Your FLV File: Drag your .flv onto the page or click "+ Add Files" to browse. Batch upload works, so several clips can be queued and converted with the same settings.
2. Choose the Video Codec: Open Advanced Options. Video Codec offers FLV — the Sorenson Spark codec Flash Player itself used — and MJPEG, and it starts on FLV. Audio Codec has one entry for this target, MP3.
3. Set Quality Preset, Video resolution, or Trim: Leave File Compression on the "Very High (Recommended)" Quality Preset, or switch to Specific file size, Constant Bitrate, Variable Bitrate, Constant Quality or Constraint Quality. Video resolution stays on "Keep original" unless you pick a preset or Width x Height, and Trim → Time Range takes a Start time and Duration.
4. Convert and Download: Click "Convert" and save the .swf. No sign-up, no watermark.

Default Output for This Conversion

Frequently Asked Questions

Is this the wrong way round — should I be converting SWF to video instead?

For most people, yes. FLV and SWF are both dead Flash formats, but SWF is the harder of the two to use: an FLV is ordinary media that VLC, mpv and FFmpeg still decode, while an SWF needs a Flash runtime that no longer exists as a supported product. Converting FLV to SWF is only worth doing when a surviving Flash pipeline demands .swf as its input. If you want a watchable file, keep the FLV or run FLV to MP4; if you already have a SWF and want video out of it, run SWF to MP4.

Can anything still play the SWF this produces?

Only emulators and preserved runtimes. Adobe ended Flash Player support on 31 December 2020 and began blocking Flash content on 12 January 2021, and Chrome, Firefox, Edge and Safari removed the plugin around the same time. What remains in practice is Ruffle, an open-source Flash Player emulator that runs as a browser extension or a desktop application, or an archived standalone Flash projector binary. Test your specific file before you rely on it playing.

What codec ends up inside the SWF?

FLV1 — the Sorenson Spark codec, an H.263 derivative — with MP3 audio, unless you switch Video Codec to MJPEG. FLV1 with MP3 is the pairing Flash Player and Adobe Animate's video import were built around, so it is the most compatible choice for an SWF. Remember that SWF is a container, not a codec: whether anything can play the file depends on both the runtime and the codec inside it.

Why did my audio come out at 44.1 kHz?

Because the SWF container only accepts three audio sample rates — 11.025 kHz, 22.05 kHz and 44.1 kHz — so our encoder pins SWF output to 44.1 kHz rather than letting an unsupported rate produce a broken file. If your FLV's soundtrack was 22.05 kHz or 32 kHz, it is resampled upward on the way in. That does not add quality, and it does not damage anything either; it just makes the stream legal for the container.

Will converting FLV to SWF reduce the quality?

Usually, yes. Many FLV files hold On2 VP6 or H.264, both meaningfully more efficient than the FLV1 that goes into the SWF, so this is normally a step down into an older codec. The picture is fully decoded and recompressed, so nothing is regained, and at an equal file size FLV1 holds less detail than H.264 did. Raise the Quality Preset or set a Constant Bitrate above the source's own to keep the loss small.

When would MJPEG be the better Video Codec choice?

When a downstream tool needs every frame independently coded — some frame-stepping, kiosk or analysis pipelines do. MJPEG stores each frame as its own JPEG with no inter-frame prediction, which makes seeking trivially cheap but makes the file much larger than FLV1 at comparable quality. If nothing in your chain asks for intra-only frames, leave Video Codec on FLV.

My SWF is bigger than the original FLV — is that normal?

It is common. If the source FLV carried H.264 or VP6, you are re-encoding into FLV1, which needs more bits for the same picture. Two things help: switch File Compression to Constant Bitrate or Specific file size and name a ceiling, and downscale under Video resolution — FLV1 grows quickly on large frames, so a 720p or 480p target is much kinder than leaving an HD source at full size.

The conversion finished but the SWF has no sound. What happened?

Check whether the source FLV had an audio track at all — silent screen captures and some stream rips genuinely do not. If it does have audio, confirm Audio Codec is on MP3 (it is the only option for this target, so it should be) and try again. Certain unusual FLV audio codecs, particularly old Nellymoser mono captures, can also fail to decode cleanly; in that case extract the audio separately with FLV to MP3 to confirm the soundtrack is intact before troubleshooting further.

How are my files handled, and how long are they kept?

Your FLV is uploaded over an encrypted connection, converted on our servers, and the .swf is returned to you. Uploads and outputs are deleted automatically a few hours after conversion — no sign-up, no watermark, never shared or made public.