Last updated June 4, 2026 (UTC)
Free online caption converter — with delivery QA
CaptionPass works as a free caption converter for SRT, WebVTT, and more — but it is built for delivery outcomes, not silent format swaps.
What you get on the free tier
- Upload-ready export tuned for your platform preset (YouTube, TikTok, HTML5, LMS, generic).
- Optional CaptionPass enhanced download with wrap, CPS, and line-length targets in the same run.
- Explainable QA report with named fixes tied to cue indices.
- No account required — 5 successful runs per UTC day per network IP.
Run your file through CaptionPass — free caption converter with a full QA report.
Convert & fix free →When a generic converter is enough
Clean source file, known-good timestamps, and you only need a different extension — a simple converter may suffice. See CaptionPass vs generic converters.
When to use CaptionPass instead
Platform upload failed, captions vanish after publish, overlaps after NLE export, or a client asked what changed — use the free tool or format-specific pages like SRT to VTT.
Convert your captions free
Upload on CaptionPass, pick a delivery preset, and download upload-ready output with optional enhanced formatting — free tier, no account required.
Convert & fix free →More guides
- SRT to VTT converter guide — headers, timestamps, and pitfallsWhen to convert SRT to WebVTT, what breaks if you rename extensions, and how to validate before HTML5 or YouTube delivery.
- SRT vs VTT — when each format silently failsComma vs dot timestamps, WEBVTT headers, and where YouTube, TikTok, and HTML5 bite.
- Caption file encoding — UTF-8, BOM, and garbled textWhy uploads show mojibake or blank cues: UTF-8 vs legacy encodings and quick fixes.
- Burned-in vs soft subtitles — what to deliver whenOpen captions burned into the picture vs separate SRT/VTT tracks — tradeoffs for editors and clients.
- Reading speed for captions — CPS, line length, and platformsCharacters per second, lines per cue, and where YouTube, TikTok, and HTML5 push back.
- YouTube caption upload issues — silent rejection and timingWhen Studio accepts a file but captions vanish: format, line length, drift, and how to validate before publish.
- YouTube rejected my SRT — invalid file and Studio errorsWhen YouTube Studio blocks an SRT upload: encoding, index gaps, bad timestamps, and how to validate before you retry.
- Caption timing drift after export from Premiere or DaVinciWhy captions slip after NLE export: frame rates, timecode starts, and how to normalize before YouTube or client delivery.
- CaptionPass vs generic subtitle convertersFormat swap tools vs delivery QA: explainable fixes, platform presets, and when each approach fits your workflow.
- CaptionPass vs Subtitle EditDesktop authoring vs delivery QA: when to use Subtitle Edit for editing and CaptionPass for platform-safe validation and API automation.
- Caption QA API for CI/CD pipelinesAutomate SRT and VTT validation in GitHub Actions or your build pipeline with POST /api/v1/process and Bearer API keys.
- TikTok subtitle format — short lines, CPS, and clean SRTVertical video reading speed, styling stripped on upload, and export settings that survive TikTok delivery.
- Why your captions are not showing — a triage guideHTML5, YouTube, and TikTok checks when subtitles vanish after upload.
- Fix overlapping subtitlesWhat overlap means and why some players drop overlapping cues.
- TTML and DFXP — broadcast-style timed text on the webNamespaces, timing, styling stripped in practice, and when TTML is the right interchange vs SRT or WebVTT.
- CaptionPass JSON IR and the developer-json presetLossless-ish cue interchange for tooling: when to use JSON IR, version tag, and how it pairs with the HTTP API.
- Timecode, frame rate, and caption syncWhy captions drift or jump: drop-frame vs non-drop, fractional frame rates, and export settings that survive upload.
- WCAG-minded captions — reading speed, sound tags, and burned-in contrastHow WCAG 1.2.x thinking maps to real files: CPS, line length, SDH-style cues, and contrast for open captions.
- Educators & classrooms — CaptionPass for instructionPartner program for instructors: API keys, workspace pilots, Learn guides, and classroom-appropriate access.
Fix in CaptionPass
Free caption converter · Homepage tool · HTTP API (v1) · Pro workspace