Skip to content

asciicast v1

asciicast v1 is a JSON-based file format for terminal sessions recorded by older versions of asciinema cli (up to 1.4).

It contains metadata, like terminal size and duration of the recording, and a series of print events (timed) that were captured during recording session.

  "version": 1,
  "width": 80,
  "height": 24,
  "duration": 1.515658,
  "command": "/bin/zsh",
  "title": "",
  "env": {
    "TERM": "xterm-256color",
    "SHELL": "/bin/zsh"
  "stdout": [
      "\u001b[1;31mHello \u001b[32mWorld!\u001b[0m\n"
      "I am \rThis is on the next line."


Every asciicast v1 includes the following set of attributes:

  • version - set to 1,
  • width - terminal width, i.e. number of columns,
  • height - terminal height, i.e. number of rows,
  • duration - total duration of the recording, as floating point number,
  • command - recorded command, as given via -c option to rec, optional,
  • title - title of the asciicast, as given via -t option to rec, optional,
  • env - map of environment variables, usually includes TERM and SHELL,
  • stdout - array of "frames", see below.


Frame represents an event of printing new data to a terminal. It is a 2 element array containing delay and data.

Delay is the number of seconds that elapsed since the previous frame (or since the beginning of the recording in case of the 1st frame) represented as a floating point number, with microsecond precision.

Data is a string containing the data that was printed to a terminal in a given frame. It has to be valid, UTF-8 encoded JSON string as described in JSON RFC section 2.5, with all non-printable Unicode codepoints encoded as \uXXXX.

For example, frame [5.4321, "foo\rbar\u0007..."] means there was 5 seconds of inactivity between previous printing and printing of foo\rbar\u0007....