Edit SRT subtitles online

No. The subtitle file is read by the page itself, and the video plays from a local reference your browser creates — it is never sent anywhere, which is also why a two-hour film opens instantly instead of uploading first. Close the tab and both are gone.

No — that is what the shift control is for. Enter -2 and every cue moves back two seconds at once, keeping the gaps between them exactly as they were. Fractions work too, so -1.5 is fine. Nothing is ever pushed below zero.

Yes to both. It reads SRT, VTT, ASS, SSA, SMI, TTML and SBV — the format is detected from the contents, so a mislabelled extension does not matter — and saves as SRT, VTT, TXT, CSV, JSON, DOCX or PDF. That makes it a converter too: open an .ass, save an .srt.

No, and knowing why saves a lot of guesswork. A constant delay — everything is two seconds late — is one shift away from fixed. A gap that grows over time is a framerate mismatch, almost always a file timed for 25 fps (PAL) played against 23.976 fps or the reverse. Shifting moves every cue by the same amount, so it can correct an offset but cannot stretch or squeeze the timeline. Check the first line and the last line against the video: if both are off by the same amount, shifting here fixes it; if the last line is much further out than the first, the file needs rescaling to the video's framerate, which is a different job.

The common guideline is at most two lines, roughly 42 characters per line, and a reading speed under about 17 characters per second — a cue should stay on screen long enough to read comfortably, with a beat to spare. After timing, this is the most frequent readability problem: a line that runs past the edge of the frame, or one that flashes by too fast. Because you edit the text and watch it against your own video here, the test is practical rather than theoretical — if you can't read a cue before it vanishes, split it into two or hold it a little longer.

Most "invalid SRT" cases come down to three things. The millisecond separator: SRT uses a comma (00:00:04,500), and a file saved with a period there is rejected by strict players. The structure: cues must be separated by a blank line and numbered in order, which manual edits can break. And the encoding: characters saved as Windows-1251 or Latin-1 show up garbled instead of throwing a hard error. Opening the file here and saving a fresh SRT rewrites it with sequential numbers, comma timestamps and clean separators, which clears the first two; garbled characters you correct on the affected lines before saving.