YouTube Chapter Timestamp Generator – Let the Arithmetic Do Itself
Writing chapters for a video description is rarely hard because of the formatting. It is hard because of the addition. You know the intro runs about a minute and three quarters and the setup runs four and a half minutes, but the description does not want lengths — it wants the second each section begins at, counted from the top of the video. Work those out by hand and you are adding minutes and seconds in your head; re-cut one section afterwards and every number below it is wrong. A YouTube chapter timestamp generator exists to remove exactly that step.
Three ways in, one list out
This tool accepts the numbers from whichever direction you happen to have them. In durations mode you type how long each section runs and the cumulative start times are worked out for you: chapter one begins at 0:00, and every later chapter begins at the sum of the durations above it. In start times mode you type the timestamps you scrubbed to in the editor and the lengths are derived as the gap to the next chapter. In paste and fix mode you drop in a block you already have, in whatever shape it arrived. Switching modes converts the list you have rather than throwing it away.
A pasted block does not have to be tidy. Lines such as 0:00 Intro, 0:00 - Intro, [0:00] Intro, 1. 0:00 Intro and Intro - 0:00 are all read correctly, with the leading list numbering, the brackets and the dashes stripped. A line with no recognisable timestamp is never silently dropped — it is collected in a short “couldn’t read these” list so you can see what was skipped and decide what to do about it.
How times are read and written
A bare number is seconds, so 90 means ninety seconds. One colon is minutes and seconds, and two colons are hours, minutes and seconds: 1:30 and 01:30 are the same value, and so are 1:02:03 and 01:02:03. In the colon forms the seconds field has to be 0–59, and in the three-part form the minutes field does too. Type 1:75 and the tool refuses it and suggests 2:15 rather than quietly accepting the value, because that pattern is far more often a typo than shorthand.
Output notation is decided once for the whole block so the column lines up. If the last chapter starts before the hour mark, every row is written M:SS. If any chapter reaches an hour, every row — including the first — gains an hours field and is written H:MM:SS, so the list starts 0:00:00 rather than mixing two notations. A pad-minutes switch gives you 00:00 throughout if you prefer it.
The timeline and the checks
Above the output, a proportional timeline draws each chapter as a segment sized by its length, so a section that swallows half the video is obvious at a glance. Segments are keyboard navigable and each one announces its title, start and length. Anything the tool has a question about is outlined and marked with an icon as well as being written out underneath, so the flag never depends on colour alone.
Genuine mistakes are reported as errors: a chapter that starts before the one above it, two chapters on the same second, a chapter with no title. The conditions YouTube sets for turning a list into chapters are reported as warnings instead, and they live in an editable panel rather than being baked in — a first chapter at 0:00, a minimum number of chapters and a minimum length per chapter, each a field you can change. Those defaults were read from YouTube’s help pages on a stated date and are not presented as permanently current; the platform can move them whenever it likes, and the panel exists so you can move with it.
Getting the block out
The finished list is shown as a monospace mockup of the description block, ready to copy in one click or download as a .txt file. A .csv export adds start, end, duration and title columns for anyone tracking sections in a spreadsheet, with every field quoted and neutralised so a title beginning with = is read as text rather than as a formula. Supply a video link or ID and the tool will also build a timestamped watch URL for each chapter, useful for pinning a comment or linking one section from elsewhere.