FLV vs H264
A detailed comparison of Flash Video and H.264 Raw Stream — file size, quality, compatibility, and which format to choose for your workflow.
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Technical Specifications
| Specification | .FLV | .H264 |
|---|---|---|
| MIME type | video/x-flv | video/h264 |
| Extensions | .flv, .f4v | .h264, .264, .avc (raw bytestream) |
| Video codecs | Sorenson Spark, VP6, H.264 (F4V) | — |
| Audio codecs | MP3, Nellymoser, AAC | — |
| Status | Deprecated since December 31, 2020 | — |
| Standard | — | ITU-T Rec. H.264 / ISO/IEC 14496-10 (AVC) |
| Typical containers | — | MP4, MKV, MOV, TS, FLV |
| Profiles | — | Baseline, Main, High, High 10, High 4:2:2, High 4:4:4 |
Strengths Comparison
.FLV Strengths
- Low overhead — the container is extremely compact.
- Designed for streaming — progressive download and seeking work well.
- Decoded natively by Flash Player on every OS for 20 years.
.H264 Strengths
- Universal hardware decode on every device since ~2010.
- 40-50% smaller than MPEG-2 at equal quality.
- Mature ecosystem with dozens of encoders (x264 is the open-source gold standard).
- Every browser, phone, TV, and car infotainment supports H.264.
- Supports everything from 144p vertical phone video to 8K HDR masters.
Limitations
.FLV — Limitations
- Flash Player is dead — no modern browser can play FLV without conversion.
- Legacy codecs (Sorenson, VP6) are poorly supported in modern tooling.
- Hardware video decoders never added FLV support.
- Metadata format is primitive compared to MP4 or MKV.
- Actively harmful to use today — every major security agency has warned against Flash since 2015.
.H264 — Limitations
- Patent-encumbered — encoding royalties apply for commercial use.
- 30-50% larger than H.265/AV1 at equivalent quality.
- Raw .h264 bytestreams have no timecode — containers (MP4/MKV) add that.
- High profiles decode slowly on pre-2010 hardware.
Frequently Asked Questions
FLV (Flash Video) is a video container format that bundles one or more video streams, audio tracks, and optional subtitles into a single file. The container format determines how metadata is organised and which codecs can live inside; the visual quality itself depends on the codec (H.264, H.265, VP9, AV1) rather than the FLV wrapper. It is part of the video files family.
H264 (H.264 Raw Stream) is a video container format that bundles one or more video streams, audio tracks, and optional subtitles into a single file. The container format determines how metadata is organised and which codecs can live inside; the visual quality itself depends on the codec (H.264, H.265, VP9, AV1) rather than the H264 wrapper. It is part of the video files family.
VLC, MPV and PotPlayer play nearly every FLV file on desktop. Browser support varies: modern Chromium, Firefox and Safari play common containers via the HTML5 <video> tag, but niche FLV variants may fail. If a device refuses your FLV, convert to MP4 with our FLV to MP4 converter for universal playback.
VLC, MPV and PotPlayer play nearly every H264 file on desktop. Browser support varies: modern Chromium, Firefox and Safari play common containers via the HTML5 <video> tag, but niche H264 variants may fail. If a device refuses your H264, convert to MP4 with our H264 to MP4 converter for universal playback.
Upload your FLV to KaijuConverter and pick MP4, MOV, MKV, WebM, or any other target. Our pipeline uses FFmpeg under the hood and stream-copies when codecs are compatible (no quality loss) or transcodes at high-quality defaults otherwise. Conversion runs server-side; both files delete within two hours.
Only when the target requires re-encoding. If the codecs inside FLV match what the target container supports, FFmpeg stream-copies the streams and the output is bit-identical to the source. Transcoding uses transparent quality defaults (CRF 20–23 H.264) and produces output indistinguishable from the original at normal viewing distance.
Working with 4K/8K Video or Files Over 100MB?
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