Subtitle Quality Checker
Find lines that are too fast to read, too long, overlapping or flashing by, using Netflix-style rules.
How it works
- 1
Drop your subtitle file into the box above.
- 2
Adjust the options; the preview updates instantly.
- 3
Download the result in the same or any other format.
Frequently asked questions
Is Subtitle Quality Checker free?
Yes. Every tool on FastSub AI is free, with no sign-up, no watermark and no usage limits.
Are my files uploaded anywhere?
No. Your files are read and processed inside your browser tab. The only downloads are the app itself and, for AI tools, the model files.
Is there a file size limit?
Subtitle files up to 20 MB and videos up to several GB, limited only by your device's memory.
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