Cut FLV

How to Cut an FLV File Online

1. Upload Your FLV File: Drag and drop, paste a URL, or click "+ Add Files" to load Flash Video clips from your computer. Batch uploads are supported, so you can queue multiple legacy YouTube rips or screen recordings at once.
2. Set Start and Duration: Enter the start time and clip length in seconds or HH:MM:SS.sss (e.g., start 00:01:12.500, duration 00:00:30.000). Use the timeline scrubber to preview the in/out points before committing.
3. Pick Output Container (Optional): FLV is kept by default so the tool can stream-copy without re-encoding when possible. If you need a modern, browser-playable file, queue the result through FLV to MP4 afterward.
4. Cut and Download: Click "Cut" — the clip is processed in your browser session and returned without watermarks, sign-ups, or queue limits.

Why Cut an FLV File?

FLV (Flash Video) was introduced on September 10, 2003 with Macromedia Flash Player 6 and became the dominant web-video container of the 2000s — early YouTube, Hulu, Vimeo, and Facebook all served FLVs over RTMP and progressive HTTP. After YouTube switched its default player to HTML5 on January 27, 2015 and Adobe ended Flash Player support on December 31, 2020, FLV stopped getting new content but didn't vanish: terabytes of FLV survive in personal archives, course-replay systems, CCTV/DVR exports, and legacy CMSes. Cutting one without first converting to MP4 keeps the original encode intact for archival fidelity.

• Trim YouTube/Vimeo rips from 2006-2014 — Tools like KeepVid, ClipNabber, and the early youtube-dl downloaded the H.263 (Sorenson Spark), VP6, or H.264 FLV stream directly. Cutting the FLV in place avoids a second-generation re-encode that would degrade the already-low source bitrate.
• Salvage CCTV / DVR clips — Many Hikvision, Dahua, and generic Chinese DVRs from 2010-2018 export evidence clips as FLV (often H.264 video with PCM or AAC audio). Pulling a 30-second segment for a police or insurance report is faster than transcoding a multi-hour recording.
• Edit screen-capture archives — Adobe Captivate, Camtasia 5-7, Jing, and ScreenFlow's older builds all saved to FLV. Cutting a specific section out of an old training recording before transcoding saves time and avoids quality loss.
• Repackage Brightcove / JW Player progressive downloads — Enterprise LMSes and corporate intranets running pre-2018 JW Player or Brightcove still ship FLV manifests. Cutting clips for slide decks or compliance reviews is a common task.
• Extract clips from Wowza / Adobe Media Server recordings — Live streams recorded by Wowza or AMS were saved as FLV (or F4V) until those products shifted defaults to MP4 around 2017. Older recordings stay FLV.
• Trim Nintendo Wii / PSP / Sony Ericsson uploads — Several mid-2000s handheld and console capture apps wrote directly to FLV with VP6 video at 320×240 or 480×272.

FLV vs MP4 — Format Comparison

Property	FLV	MP4
Released	September 10, 2003 (Macromedia / Adobe)	2001 (ISO/IEC 14496-14, ISO base media file format)
Typical video codecs	Sorenson Spark (H.263), On2 VP6, H.264 (Flash 9.0.115+, Dec 3, 2007)	H.264, H.265/HEVC, AV1, MPEG-4 ASP
Typical audio codecs	MP3, AAC (Flash 9+), Nellymoser Asao, ADPCM, Speex, PCM	AAC, MP3, ALAC, Opus, AC-3
Max audio sample rate	44.1 kHz	48 kHz+ (codec-dependent)
Browser playback (2026)	None natively; needs conversion or FFmpeg-WASM player	Universal in Chrome, Firefox, Edge, Safari
Metadata for seeking	Requires onMetaData keyframe index injection (yamdi/FLVMDI)	Native moov atom; faststart for progressive HTTP
Streaming protocol	RTMP, RTMPE, HTTP progressive (now legacy)	HLS, DASH, HTTP progressive
Status (2026)	Legacy / archival only — Flash Player EOL Dec 31, 2020	Active web/mobile standard

FLV Codec Quick Reference

Internal video codec	When used	Cut behavior
Sorenson Spark (H.263)	Flash Player 6-7 era (2003-2005); early YouTube uploads	Stream-copy safe; very small keyframe distance, near-frame-accurate cuts
On2 VP6	Flash Player 8 (Aug 2005) until H.264 era; better quality than Spark at the same bitrate	Stream-copy safe; intra-period typically 2-10 s, cuts snap to nearest keyframe
H.264 / AVC	Flash Player 9.0.115.0 (Dec 3, 2007) onward; YouTube/Vimeo HD FLV streams	Stream-copy safe; modern players read it; GOP often 2-10 s
Screen video (SWF)	Camtasia/Captivate screen recordings	Stream-copy safe but uncommon in non-Adobe tools

Frequently Asked Questions

Will cutting my FLV re-encode the video and reduce quality?

When the cut points align with existing keyframes (I-frames), the tool can stream-copy the video and audio bitstreams without re-encoding, preserving the original quality bit-for-bit. If your in/out times fall between keyframes — which is common for VP6 and H.264 FLVs with 2-10 second GOP lengths — the cut will either snap to the nearest keyframe (lossless but slightly off-time) or re-encode a small bridging segment. For Sorenson Spark / H.263 FLVs from 2003-2005 the keyframe cadence is much tighter, so frame-accurate lossless cuts are usually possible.

Why won't my browser play the FLV directly?

No mainstream browser has shipped a native FLV decoder since Chrome and Firefox dropped NPAPI plugin support in 2015-2017, and Adobe ended Flash Player itself on December 31, 2020. Modern browsers can only play MP4 (H.264/H.265), WebM (VP8/VP9/AV1), and Ogg natively. To watch the file inside a browser, convert it with FLV to MP4 or FLV to WebM; the bitstream itself is still good, you're just changing the container and possibly the video codec.

Can I cut a 2 GB+ FLV file recorded by Wowza or Adobe Media Server?

Yes. The browser session streams chunks rather than loading the whole file into memory, so multi-gigabyte FLVs from long-form Wowza, Adobe Media Server, or Red5 recordings work the same as small clips. Long live-stream recordings sometimes have missing or corrupt onMetaData tags, in which case seeking by absolute time is slower — for those, set the cut points by byte offset or run the file through yamdi -i in.flv -o out.flv first to re-inject a keyframe index.

My FLV plays in VLC but other tools say it's broken — what's going on?

VLC ships its own FLV demuxer that's very forgiving of missing or corrupt metadata tags, partial GOPs, and stream-mux quirks left by RTMP recorders. Stricter parsers (Windows Movie Maker, Premiere Pro CC, mainstream online cutters) refuse files that VLC happily plays. Running the source through FFmpeg with -c copy -bsf:a aac_adtstoasc (for AAC) or yamdi first usually repairs the metadata enough for downstream tools — or convert to MP4 first via FLV to MP4 and edit that.

Should I cut the FLV first, or convert to MP4 first and cut that?

Cut the FLV first if archival fidelity matters (e.g., legal evidence, an irreplaceable family video, a YouTube classic that's no longer online). Stream-copying preserves the exact original encode. Cut after converting if you need frame-accurate edit points, multiple cuts per file, or you'll be re-encoding anyway for a different target (e.g., trimming for a YouTube re-upload that'll be transcoded server-side). For batch work on dozens of files, Compress FLV lets you re-encode to a smaller size in the same pass.

How do I handle Nellymoser audio in cut FLV files?

Nellymoser Asao was Macromedia's proprietary microphone-recording codec (32-bit float, 8/11/22 kHz) used in Flash apps that captured live audio — webcam recorders, voicemail apps, early Flash chat rooms. It's still streamable inside FLV, so cutting works fine, but very few players outside VLC and FFmpeg decode it. If you need wider compatibility after the cut, re-encode the audio track to AAC or MP3 — most modern toolchains will do this automatically when you convert the container to MP4.

Does the cut FLV keep its original timestamps and metadata?

The video and audio timestamps are rewritten to start at zero (so the clip plays from 00:00), but other onMetaData fields (duration, width, height, framerate, videocodecid, audiocodecid) are recalculated for the trimmed range. Custom AMF cue points used by interactive Flash applications and chapter markers are not preserved — those were Flash-specific and don't map to anything in modern players. If you need cue points in the output, transcode to MP4 and add chapter markers there.

Can I extract just the audio from an FLV instead of cutting video?

Yes — for that use case FLV to MP3 extracts the audio stream directly. If the source already has MP3 audio (common in pre-2007 FLVs), it's a lossless mux. If it's AAC, Nellymoser, or Speex, you'll get a decode + re-encode. Cut the FLV first if you only need the audio from a specific segment, then extract.

Is FLV still used anywhere new in 2026?

Almost nowhere for new production. Twitch and the Chinese live-streaming ecosystem (Bilibili, Douyu) still ingest live streams as RTMP-with-FLV-payload because the format multiplexes audio and video tags with very low latency, but the delivered output is always HLS or DASH MP4. Some niche tools — OBS Studio's FLV recording option, older Wirecast versions, certain IP camera firmwares — still write FLV files. For everything else, MP4, WebM, and MKV have replaced it.