Summary
- Subtitle QA is the sign-off before a file leaves you: does it meet the client's spec, read well against the picture, and open cleanly wherever it's going?
- Run it in a fixed order: spec, structure, timing, readability, encoding, then a review against the video. Fix, then re-check from the top.
- The best subtitle QC software splits the job: a checker that lists every problem by cue number, and a fixer that repairs only what can be repaired safely.
- Check your subtitle file free in the SRT validator, no account needed, then repair it in Fix Subtitles.
Fixing a broken subtitle file and signing off a finished one are different jobs. Fixing starts from a known problem. QA starts from a file you think is ready and asks whether a strict reviewer would agree. A file can pass a quick look and still fail a check nobody ran.
This guide sets out the subtitle QA tools, including free subtitle QC software, and the checks to use before delivery in 2027, for freelancers, agencies and in-house teams. If you already know the file is broken, start with how to fix an SRT file online instead.
Run a free subtitle check now: open the SRT validator. It runs in your browser and lists every problem by cue number.
Step 1: Write down the spec before you check anything
QA is checking against something. Before you open the file, note the client's or platform's requirements:
| Spec item |
Example of what to note |
| File format |
SRT or VTT; character encoding if stated |
| Characters per line |
The client's limit, if different from 42 |
| Reading speed |
The client's characters-per-second limit, if different from 20 |
| Lines per cue |
Usually two at most |
| Minimum cue duration and gaps |
Any minimum display time or gap between cues |
| Text conventions |
Italics, speaker identification, sound descriptions, numbers |
| File naming |
Language codes, version numbers |
If the spec sets different limits than VideoText's defaults, the spec wins. Our CPL and CPS benchmarks by style guide show how specs differ, and the list of every check and threshold shows where each VideoText default comes from.
Step 2: Run the automated subtitle QC checks
Open the file in the free SRT validator. It runs in your browser with no account, and the file is never uploaded. It reports by line or cue number:
- Structure: unreadable timing lines, a dot instead of a comma in timestamps, missing hours, missing blank lines between cues, wrong or repeated cue numbers, empty cues and text before the first cue.
- Timing: captions that end before they start or never show, overlapping captions, cues out of time order, and tiny gaps that make captions blink.
- Readability: lines over 42 characters, more than 20 characters per second, and captions on screen for under 0.8 seconds.
- Encoding: garbled accents that can be recovered, and characters already lost.
Read errors before warnings. Errors stop imports or show the wrong caption; warnings are readability problems that won't stop a file being accepted but may fail a reviewer. To check a single cue's reading speed by hand, use the reading-speed calculator.
Step 3: Repair, then re-check from the top
Repair what the checks found:
- Structure and encoding: the validator's one-click repair makes only changes with one correct answer, such as timestamp format, numbering, blank lines and recoverable characters. It never rewrites dialogue or guesses at timing.
- Timing and readability: Fix Subtitles ends overlapping cues before the next one starts, re-wraps text onto at most two lines of 42 characters, and gives cues faster than 20 characters per second more time where the next cue allows it, up to 10 seconds per cue. It doesn't change wording, and lists anything it can't repair safely with where it is.
Then run the validator again from the top. A repair in one place can move a problem to the next cue.
Repair what the checker found: upload the file to Fix Subtitles. It fixes overlaps, long lines and fast cues without changing wording.
Step 4: Review against the video
Automated checks can't tell you whether the words are right or the timing feels right. Watch the file with the picture:
- Sync: do cues appear when the speech starts and leave when it ends?
- Scene cuts: cues that cross a camera cut are distracting. With the source video, Fix Subtitles flags cues that cross a cut.
- Wording: names, numbers, terms and anything the client will quote.
- Line breaks: do lines break at natural points in the sentence?
- On-screen text: do captions cover titles or lower thirds?
In Video to Subtitles you can play each cue against the video with overlaps and fast cues flagged; editing cues there is a Pro feature. For ways to cut review time, see how to reduce QA time on subtitles before client delivery.
Step 5: QA every language and every version
- Translations: translated lines often run longer, so line length and reading speed can fail even though timing is unchanged. Re-run the checks on each language. Translate Subtitles keeps every cue's timing and points out lines that look untranslated or mixed-language.
- Burned-in versions: once captions are in the picture, a fix means rendering again. QA the subtitle file before you burn it in, then watch the burned-in video start to finish.
Step 6: Sign off and deliver
Keep a short record with each delivery: the spec you checked against, a clean validator report or a note on each remaining item, and the version delivered. If a client questions the file later, you have the evidence.
Subtitle QC sign-off checklist
What it costs
The validator is free with no account. Fix Subtitles needs a free account to fix and download; free downloads include two short VideoText watermark cues, one at the start and one after the last cue. Pro is $14.99/month or $120/year and adds cue editing, PDF and Word export, and no watermark. See pricing.
FAQ
What's the difference between subtitle QA and fixing subtitles?
Fixing repairs known problems. QA is the sign-off on a file you think is ready, against the client's spec and the video.
Which subtitle QC checks can be automated?
Structure, timing, readability limits and encoding. Wording, sync feel, scene cuts and on-screen text need a review against the video, though scene cuts can be flagged when you add the source video.
What limits should I check against?
The client's or platform's spec. VideoText's defaults are 42 characters per line and 20 characters per second.
Should I QA before or after burning in captions?
Before, then watch the burned-in video once more. Fixing a video from Burn Subtitles means rendering it again.
What is the best free subtitle checker?
One that lists every problem by cue number and runs without an upload. The SRT validator checks structure, timing, readability and encoding in your browser, free and with no account.
Next step
Open your next delivery in the free SRT validator with the client's spec next to it, repair what it finds in Fix Subtitles, and work through the checklist. Free downloads carry two short watermark cues; for client delivery, Pro removes them and adds cue editing for $14.99/month or $120/year. If the file is going into the picture next, see how to burn subtitles into video. This guide is part of Best subtitle software in 2027 and Subtitle and transcription tools: the 2027 guide.
Sources: VideoText SRT validator, Fix Subtitles, Video to Subtitles, Translate Subtitles and pricing pages, https://videotext.io/tools/subtitle-validator, https://videotext.io/fix-subtitles, https://videotext.io/video-to-subtitles, https://videotext.io/translate-subtitles and https://videotext.io/pricing, https://videotext.io/burn-subtitles, https://videotext.io/tools/subtitle-reading-speed (checked October 25, 2026; rechecked October 28, 2026).