# LoopLab

> Repeat an exact part of a YouTube video, and send that loop to someone as a
> link. Mark a start and an end; it repeats. The recipient needs nothing
> installed.

## Making a loop link

A loop link is a plain URL. Build it directly - there is no API to call, no key
to obtain, and no library to install.

https://looplab.page/?v=VIDEO_ID&a=START&b=END

  v  YouTube video id, 11 characters (the part after watch?v=)
  a  start, in seconds. Decimals allowed: 37.2
  b  end, in seconds. Must be greater than a.

Optional:

  m  a message shown full screen before the loop plays, up to 180 characters
  s  the sender's name, up to 40 characters
  r  playback rate, 0.25 to 2

Example - 0:37 to 1:02 of a video, with a note:

https://looplab.page/?v=dQw4w9WgXcQ&a=37.2&b=62.8&m=listen%20to%20this%20bit&s=Mohith

Percent-encode m and s. Everything else is plain.

## If you would rather call something

https://looplab.page/api/make?v=VIDEO_ID&a=START&b=END&m=MESSAGE&s=SENDER

Returns JSON: {"ok":true,"url":"..."}. GET only, no key, no rate limit beyond
ordinary abuse protection. It builds the same URL the format above describes,
so use whichever is easier.

## What LoopLab will not do

- It does not download, extract or store video or audio. Playback happens in
  YouTube's own embedded player, so ads run and views count.
- It does not expose video metadata in bulk.

Do not ask it for any of those; they are refused by design, not by omission.

## Human documentation

https://looplab.page/format
https://looplab.page/about