How to use the subtitle quality checker
Start with the subtitle text or file, then inspect the report before changing anything. A row identifies the cue, timestamp, rule, severity, issue, and suggested fix, so a timing error stays separate from a whitespace notice.
How to validate SRT and WebVTT subtitles
- Paste subtitle text into Paste subtitle content below, or drop/upload a file:, or select browse files.
- Choose Auto-detect, SRT, or WebVTT under Format. In auto-detect mode, text starting with
WEBVTTis parsed as WebVTT. - Select a QC profile: Netflix (English, approximate), BBC guidelines (approximate), Generic / relaxed, or Custom.
- Load a dictionary through Spelling dictionary (optional) if you want spelling issues. Use one word per line in a
.txtor.dicfile. - Read the Validation report, then choose Export JSON, Export CSV, or Preview corrected file.
What the subtitle QC profiles and thresholds change
A selected QC profile fills seven fields: Max chars/second, Max words/minute, Max line length, Max lines per cue, Min cue duration (ms), Max cue duration (ms), and Min gap between cues (ms). Choose Custom to edit them. The report also checks overlaps, start-time ordering, numbering, empty cues, timestamps, tags, and whitespace.
For example, this cue has two spaces:
1
00:00:01,000 --> 00:00:04,000
Hello there.
Report: Cue 1 | Whitespace | info
Issue: Line 1 has repeated spaces.Repeated spaces appear as an informational whitespace issue. The suggested fix says to collapse them, while the source stays unchanged until you select Preview corrected file. With a loaded dictionary, an unmatched word is also informational and is left for review.
What subtitle validation leaves unchanged
A malformed cue block is reported, then excluded from later cue-level checks. The corrected file is created only after you select Preview corrected file. It keeps timestamps and cue order, normalizes whitespace, renumbers serialized SRT cues, and closes unclosed <b>, <i>, and <u> tags.
- Select Export JSON or Export CSV to save the report.
- Select Download corrected file only after checking the preview.
- Malformed or excluded blocks are omitted from the serialized output. WebVTT
NOTE,STYLE, andREGIONmetadata may also be omitted.
What the report can show
Timing checks cover cue duration, gaps, overlaps, and start-time ordering. Text checks cover reading speed, line length, line count, empty cues, tags, and whitespace. Numbering issues appear for numeric SRT identifiers that do not match their cue position.
Spelling checks run only after a dictionary is loaded. The dictionary is read as lowercase words split by line. Uppercase acronyms and words containing digits are skipped, while an absent word is shown as an informational issue.
When to use subtitle validation
Use Subtitle Validate Tools for rule-based checks on an existing SRT or WebVTT file. This page reports issues against a selected profile or your own thresholds, then lets you review formatting-only corrections. It does not translate subtitles or render captions onto video.
The page reads subtitle and dictionary files in the browser with local file access. Its code makes no upload request for those files. A subtitle file longer than 400,000 characters is shortened in the text-area preview, while the full source is used for the initial validation.
Frequently asked questions
Can I validate an SRT or WebVTT file here?
Yes, you can paste subtitle content or select an SRT or WebVTT file. Choose Auto-detect, SRT, or WebVTT under Format.
What does the subtitle quality checker report?
It reports timing, reading speed, line length, line count, cue duration, gaps, overlaps, ordering, numbering, empty cues, tags, whitespace, and optional spelling issues.
How do I run a spelling check on subtitles?
Load a plain-text dictionary with Spelling dictionary (optional). The file is read one word per line, and words absent from it are shown as informational issues.
Does the corrected subtitle file change my wording?
No, the corrected output keeps wording, timestamps, and cue order. It applies formatting cleanup, SRT renumbering, and closing for unclosed <b>, <i>, and <u> tags after you choose Preview corrected file.
Does subtitle validation upload my file?
The page reads subtitle and dictionary files in your browser, and its local code does not send those files in an upload request. A file over 400,000 characters is truncated in the text-area preview, while the full source is used for the initial validation.