MP4 to SWF Converter

How to Convert MP4 to SWF Online

1. Upload Your MP4 File: Drag and drop, or click "+ Add Files" to pick MP4 (or M4V) files from your computer. Batch conversion is supported — queue several clips and they process in sequence.
2. Pick Video Codec and Quality Preset: Default codec for SWF output is FLV1 (Sorenson Spark / H.263-based) — the codec Flash Player itself used for video tags. MJPEG is also offered when you need every frame intra-coded for editing. Set Quality Preset (Highest, Very High, High, Medium, Low, Very Low, Lowest), target a Constant Bitrate, an exact file size in MB/KB, or a percentage of the source size.
3. Resize, Trim, or Set Audio (Optional): Choose a Preset Resolution (4K, 1440p, 1080p, 720p, 480p, 360p, 240p, 144p, plus square and 9:16 vertical presets), scale by percentage, or enter custom Width×Height. Trim by start time and duration. For audio inside SWF, pick MP3 (the canonical Flash audio codec) or ADPCM-SWF; set bitrate if needed.
4. Convert and Download: Click Convert. Files process in your browser session — no sign-up, no watermark, no email required.

Why Convert MP4 to SWF?

SWF (originally "ShockWave Flash", later rebranded "Small Web Format") was the file container for Adobe Flash content from 1996 until Adobe's Flash Player end-of-life on December 31, 2020. Adobe blocked all Flash content from running in Flash Player on January 12, 2021, and every major browser removed the Flash plugin shortly after. For new web video, MP4 (H.264/AAC) is the right answer in essentially every case. Converting MP4 to SWF only makes sense when you have a legacy pipeline that still consumes SWF as input — be honest about that before you convert.

• Adobe Animate projects that still target SWF — Adobe Animate (the rename of Flash Professional in February 2016) is in maintenance mode but still officially exports the SWF and AIR formats. If your team imports video into an Animate timeline that publishes to SWF, an FLV1-encoded SWF is what the import expects.
• Legacy CD-ROM, kiosk, and museum installations — many standalone projector-based exhibits built before 2020 still play SWF through a bundled Flash projector binary, and updating the source assets requires a SWF input.
• Flash-based e-learning packages (SCORM 1.2 / 2004) — older LMS courses authored in Captivate, Articulate Presenter, or Lectora often package SWF assets that must remain in the original format until the course is rebuilt for HTML5.
• Ruffle-hosted preservation archives — projects like the Internet Archive's Flash collection rely on the Ruffle emulator (MIT/Apache-2.0 licensed, written in Rust) to play SWFs in modern browsers. Video-bearing SWFs are still a work in progress in Ruffle, so test playback before you commit.
• Game-preservation and modding workflows — many late-2000s Flash games shipped as SWF wrappers around FLV1 video cutscenes; replacing those cutscenes with new footage requires re-encoding MP4 back to SWF.

For new presentations, training, or web embeds, convert MP4 to MP4 (re-encode with Compress MP4) or MP4 to WebM instead — both play natively in every modern browser without an emulator.

SWF vs MP4 vs HTML5 Video

SWF Video Codec Quick Guide

SWF is a container, not a codec — what plays back depends on which video codec is embedded.

If you don't know what the target SWF consumer expects, FLV1 is the safest default — it's what Flash Player itself used and what Animate's video import expects.

Frequently Asked Questions

Can modern browsers play the SWF file I create?

No. Adobe blocked Flash content in Flash Player on January 12, 2021, and Chrome, Firefox, Edge, and Safari removed the Flash plugin around the same time. To play an SWF today you need the Ruffle emulator (browser extension, desktop app, or WebAssembly embed) or a preserved standalone Flash Projector binary. If browser playback matters, keep the file as MP4.

Does Ruffle play the video inside my converted SWF?

Often not yet. Ruffle's ActionScript coverage is high (around 99% of AS1/AS2 and roughly 90% of AS3 language features as of 2026), but video tags inside SWF — especially anything beyond plain FLV1 — are still an incomplete area of the emulator. Test your specific SWF in Ruffle before relying on it; for guaranteed playback, keep the original MP4.

Why is my MP4 still useful and SWF basically isn't?

MP4 (ISO/IEC 14496-14) is the modern, standardized container that every browser, phone, TV, and editing app reads natively. SWF was tied to a single vendor's plugin that has been end-of-life for over five years. Convert to SWF only when a specific legacy tool demands it; convert from SWF whenever you can with SWF to MP4.

Which codec should I pick — FLV1 or MJPEG?

FLV1 (Sorenson Spark) for almost every case. It's the codec that Flash Player and Adobe Animate's video import were designed around, and it produces reasonable file sizes. Pick MJPEG only when a downstream tool explicitly needs intra-only frames (every frame independently encoded), at the cost of much larger output.

Can Adobe Animate still open the SWF I generate?

Yes. Adobe Animate (renamed from Flash Professional in February 2016) is in maintenance mode but still officially supports publishing to SWF and AIR. Imported video inside an Animate timeline expects FLV1, so use that codec when targeting Animate.

Will the converted SWF be larger or smaller than the source MP4?

Usually larger, sometimes much larger. SWF's typical video codecs (FLV1, VP6) are 15-20 years older than H.264 and compress less efficiently at the same visual quality. Use the Constant Bitrate or Specific File Size option if you need to keep output under a particular cap.

Can I trim the MP4 before converting to SWF?

Yes. Expand the Trim option, set a start time and duration in HH:MM:SS.mmm, and only the trimmed segment is encoded into the SWF. Use the dedicated Video Cutter if you need finer control or multiple segments.

Is there a file-size limit?

Files process in your browser session, so the practical limit is your device's available memory and how long you're willing to wait. Long 1080p MP4 inputs re-encoded to FLV1 can grow significantly; trim or downscale to 720p/480p first if the SWF needs to stay compact.

Are MP4 and SWF really interchangeable?

No. SWF is a vector-and-scripting container that can hold video; MP4 is a video-and-audio container with no scripting. A converted SWF only contains the video stream — you can't roundtrip an SWF that had ActionScript, vector graphics, or interactivity through MP4 and back without losing all of that.