Convert FLV to captions

Create accessible closed captions from your FLV videos. Bring legacy Flash content into accessibility compliance with professional captions.

Free to start — no credit card required.See pricing

ADA compliant
5-min turnaround
Accessible
FLV conversion guide

Create captions from FLV in 6 steps

  1. 1
    Create account~30 sec

    Sign up for a free Sonix trial with 30 free minutes.

  2. 2
    Upload file~1 min

    Upload your FLV file from your computer or cloud storage.

    44+ formats supported
  3. 3
    Select language~10 sec

    Select the language spoken in your file.

    54+ languages
  4. 4
    Auto-transcribe~5 min

    Sonix AI transcribes your FLV with word-level timestamps.

  5. 5
    Edit captions~2 min

    Fine-tune timing and formatting for accessibility.

  6. 6
    Export~10 sec

    Download your closed captions as SRT or VTT files.

    30+ export formats
The FLV file format

Understanding FLV files

What is a FLV file?

Legacy Flash video format for web streaming

FLV files are also known as Flash Video Files. Most FLV files use Adobe Flash Player or Adobe Air to transmit audio/video over the Internet. Most embedded videos on the Internet are FLV files, but with the introduction of HTML5 videos, many streaming services have dropped usage of FLV files. You can sometimes see FLV files with a F4V file extension. FLV files aren’t as common now, but we still support them at Sonix.

Common uses for FLV files

  • Legacy web videos
  • Archived Flash content
  • Old streaming platforms
  • Legacy YouTube downloads
  • Archived web content
  • Old streaming sites

Who works with FLV files?

Digital archivists, e-learning teams, and media librarians maintaining Flash-era video libraries still work with FLV files, often while migrating old training courses, webinars, and news clips to modern formats. Researchers and journalists reviewing pre-2015 web footage also encounter FLV files in their source material.

FLV vs MP4: which should you use?

FLV is a legacy container tied to Adobe Flash Player, while MP4 is an open ISO standard supported natively by browsers, phones, and editing software. FLV files often use older codecs such as Sorenson Spark or On2 VP6, whereas MP4 typically pairs H.264 video with AAC audio. Choose MP4 for anything you plan to play, share, or edit today; FLV is mainly relevant when handling archived Flash-era content.

Convert MP4 to text
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Get your FLV captions in minutes
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Accuracy rate
Industry-leading AI for FLV files
53+
Languages
Captions in any language
30+
Export formats
SRT, VTT, and TTML
FLV conversion FAQ

FLV captions: frequently asked questions

What's the difference between captions and subtitles for FLV?

Captions include speaker identification and sound descriptions (music, applause, typing sounds) for deaf and hard-of-hearing viewers. Subtitles assume the viewer can hear and focus on translating dialogue.

Can I make archived FLV content ADA compliant?

Yes! Sonix generates captions meeting ADA and Section 508 requirements. Add speaker labels and sound descriptions to bring legacy Flash content into compliance.

Can I add sound descriptions to FLV captions?

Yes! After transcription, add non-speech descriptions like [music playing], [static noise], or [applause] in Sonix's editor for fully accessible captions.

How do I create accessible captions for archived FLV content?

Upload FLV, transcribe with Sonix, add speaker labels and sound descriptions, then export captions. Convert video to MP4 for modern accessible playback.

What caption format works for FLV in modern archives?

SRT is most universal for archival purposes. Include SRT files alongside your FLV archives (or converted MP4s) for accessibility.

How accurate are AI-generated captions from old FLV?

Accuracy depends on audio quality, not file age. FLV files with clear speech transcribe at 99%+ accuracy. Lower-bitrate audio from early web videos may have slightly reduced accuracy.

Why won't my FLV file play on my computer?

FLV was designed for Adobe Flash Player, which was discontinued at the end of 2020, so modern browsers and many media players no longer support it. Players such as VLC can still open FLV files, or you can convert them to MP4 for broader compatibility.

Do I need to convert FLV to MP4 before transcribing?

No, FLV files can be uploaded directly for transcription. Converting to MP4 is only needed if you also want the video to play in modern browsers or editing software.

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