Use in your browser
Check one WebVTT, SRT, or TTML caption file against the real spec parsers: cue timing, overlaps, encoding, and reading speed in CPS. Compare two tracks to see where cue counts and timing drift apart.
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Guest access is available after setup. Full account linking verified by PowMCP: Claude only.
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For clients that require manual configuration, use this app-only endpoint, its JSON entry, or one terminal command.
ChatGPT: enable Developer mode in Settings → Security and login, then add this MCP endpoint from the Plugins page. Availability depends on your account and workspace policy. PowMCP has not yet verified ChatGPT account linking. OpenAI setup guide
https://powmcp.com/caption-file-check/mcp {
"mcpServers": {
"powmcp-caption-file-check": {
"type": "http",
"url": "https://powmcp.com/caption-file-check/mcp"
}
}
}Terminal agents add this app with one command:
claude mcp add --transport http powmcp-caption-file-check https://powmcp.com/caption-file-check/mcpcodex mcp add powmcp-caption-file-check --url https://powmcp.com/caption-file-check/mcpgemini mcp add --transport http powmcp-caption-file-check https://powmcp.com/caption-file-check/mcpManage, disable, or remove this connection in your agent's own MCP settings. PowMCP does not label an external connection as installed without confirmation from that client.
Proof
Check subtitle and caption files in chat
Preflight a WebVTT, SRT or TTML/IMSC caption file from a chat attachment or public URL for format conformance, encoding, in-file cue timing and overlap, line length and reading speed against a named profile, or compare two tracks for cue-count and timing drift under identical limits. Internal timing checks do not verify alignment with spoken audio or video. A pass reflects the selected file checks and profile; it does not establish platform acceptance.
Request cost1 completed result
Guests get 50 lifetime app requests. Free accounts get 100 each calendar month.
caption_check
Preflight one caption or subtitle file before delivery. Attach a WebVTT (.vtt), SRT (.srt), or TTML/IMSC (.ttml/.xml) caption file in chat or give a publicly fetchable URL and it downloads the artifact under an SSRF-guarded, 2 MB-capped fetch, detects the format by content and the byte encoding and BOM, then parses it with the real spec engine (the WebVTT spec parser, a dedicated SRT parser, or the imscJS TTML/IMSC profile engine) and returns deterministic evidence: pass/fail, cue count, structural spec and IMSC profile-conformance errors, overlapping / negative / out-of-order / empty cues, per-line length, and per-cue and summary reading speed (CPS) against a named platform profile (netflix-adult-20, netflix-children-17, youtube, ebu-tt). It reports only source-file conformance, timing, encoding, and reading-speed facts against a dated profile. It does not judge translation quality, transcription accuracy, or synchronization against the video. An arbitrary XML or text file that is not a caption track returns an explicit unsupported-format error. Fetching and parsing a full-length track can take up to 60 seconds.
caption_compare
Compare exactly two caption or subtitle files under identical bounded checks: an original versus its translated track, before versus after a timing fix, or a format migration. Attach two WebVTT, SRT, or TTML/IMSC caption files in chat or give two publicly fetchable URLs and it runs the same SSRF-guarded, 2 MB-capped preflight as caption_check on each, then aligns them by cue index and reports side-by-side pass status, detected-format and encoding differences, the cue-count delta, timing drift and overlap differences, reading-speed (CPS) regressions, structural-error deltas, and a winner only when the measured checks separate the two. Use caption_check for a single file. It reports only source-file conformance, timing, encoding, and reading-speed facts against a dated profile: never translation quality, transcription accuracy, or sync against the video. Fetching and parsing two live files can take up to 60 seconds.
Other apps for the jobs next to Caption File Check.
Scope and boundaries for Caption File Check.
Check the W3C English WebVTT sample with the Netflix adult 20-CPS profile, or compare its English and French tracks by URL to inspect cue-count and timing drift.
Start with pass and structuralErrorCounts. Pass means at least one cue was checked with no structural, timing, line-length, or reading-speed failure under the selected profile. Fix structural and timing errors first; treat cue-cap truncation or an unpreflighted comparison file as incomplete, and remember that comparison aligns cues by index without assessing transcription, translation, or video sync.
This is a source-file, timing, encoding, and named-profile reading-speed preflight. It does not evaluate translation quality, transcription accuracy, caption meaning, or synchronization against the actual video, and files are bounded to 2 MB.