Web player for terminal session recordings
Clojure CSS HTML JavaScript


asciinema player

Build Status

Web player for terminal session recordings (as produced by asciinema recorder) that you can use on your website by simply adding <asciinema-player> tag.


asciinema player is an open-source terminal session player written in ClojureScript. Contrary to other "video" players asciinema player doesn't play heavy-weight video files (.mp4, .webm etc) but instead it plays light-weight terminal session files called asciicasts (simple .json files).

Asciicast is a capture of terminal's raw output and thus the player comes with its own terminal emulator based on Paul Williams' parser for ANSI-compatible video terminals. It covers only the display part of the emulation as this is what the player is about (input is handled by your terminal+shell at the time of recording anyway) and its handling of escape sequences is fully compatible with most modern terminal emulators like xterm, Gnome Terminal, iTerm, mosh etc.

You can see the player in action on asciinema.org.

If you don't want to depend on asciinema.org and you prefer to host the player and the recordings yourself then read on, it's very simple.


  • HTML5 <asciinema-player> element you can use in your website's markup,
  • copy-paste of terminal content (it's just a text after all!),
  • predefined and custom font sizes,
  • custom playback speeds,
  • looped playback,
  • starting playback at specific time,
  • keyboard shortcuts,
  • multiple color schemes for standard 16 colors,
  • 256 color palette / 24-bit true color (ISO-8613-3),
  • full-screen mode.

Self-hosting quick start

The following example shows how to use asciinema player on your own website, without depending on asciinema.org.

It assumes you have obtained terminal session recording file by either:

Download the player

Download latest version of the player from releases page. You only need asciinema-player.js and asciinema-player.css files.

Use the player in your HTML page

First, add asciinema-player.js, asciinema-player.cssand the .json file with your recording to your site's assets.

Then add necessary includes to your HTML document:

  <link rel="stylesheet" type="text/css" href="/asciinema-player.css" />
  <asciinema-player src="/demo.json"></asciinema-player>
  <script src="/asciinema-player.js"></script>

<asciinema-player> element attributes


Number of columns of player's terminal.

When not set it defaults to 80 (until asciicast gets loaded) and to terminal width saved in the asciicast file (after it gets loaded).

It's recommended to set it to the same value as in asciicast file to prevent player to resize itself from 80x24 to the actual dimensions of the asciicast when it gets loaded.


Number of lines of player's terminal.

When not set it defaults to 24 (until asciicast gets loaded) and to terminal height saved in the asciicast file (after it gets loaded).

Same recommendation as for cols applies here.


Set this attribute to any value if playback should start automatically. Defaults to no autoplay.


Set this attribute to any value if the recording should be preloaded on player's initialization. Defaults to no preload.


Set this attribute to any value if playback should be looped. Defaults to no looping.


Start playback at given time.

Supported formats:

  • 123 (number of seconds)
  • 2:03 ("mm:ss")
  • 1:02:03 ("hh:mm:ss")

Defaults to 0.


Playback speed. Defaults to 1 (normal speed). 2 means 2x faster.


Poster (preview) to display before playback start.

The following poster specifications are supported:

  • npt:2:34 - show recording "frame" at given time
  • data:text/plain,Poster text - show given text

The easiest way of specifying a poster is to use npt:2:34 format. This will preload the recording and display terminal contents from the recording at 2 min 34 s.


<asciinema-player src="..." poster="npt:2:34"></asciinema-player>

Alternatively, a poster value of data:text/plain,This will be printed as poster\n\rThis in second line will display arbitrary text. All ANSI escape codes can be used to add color and move the cursor around to produce good looking poster. You need to replace usual \xXX hex syntax with Unicode \u00XX though.

Example of using text poster with cursor positioning:

<asciinema-player src="..." poster="data:text/plain,I'm regular \u001b[1;32mI'm bold green\u001b[3BI'm 3 lines down"></asciinema-player>

Defaults to screen contents at start-at (or blank terminal when start-at is 0).


Size of the terminal font.

Possible values:

  • small
  • medium
  • big
  • any CSS font-size value (e.g. 15px)

Defaults to small.


Terminal color theme.

One of:

  • asciinema
  • tango
  • solarized-dark
  • solarized-light
  • monokai

Defaults to asciinema.


Title of the asciicast, displayed in the titlebar in fullscreen mode.


Author of the asciicast, displayed in the titlebar in fullscreen mode.


URL of the author's homepage/profile. Author name (author above) is linked to this URL.


URL of the author's image, displayed in the titlebar in fullscreen mode.

Example usage with options

<asciinema-player src="/demo.json" speed="2" theme="solarized-dark" loop="loop" poster="data:text/plain,\u001b[5;5HAwesome \u001b[1;33mdemo!"></asciinema-player>

Controlling the player programmatically

The player's DOM element provides several properties, methods and events mimicking HTMLVideoElement, allowing for programmatical control over the player.



duration property gives the length of the recording in seconds, or zero if no recording data is available (for ex. before loadedmetadata event is triggered).

document.getElementById('player').duration; // 123.45


currentTime property gives the current playback time in seconds. Setting this value seeks the recording to the new time.

document.getElementById('player').currentTime; // 1.23
document.getElementById('player').currentTime = 33;



play method attempts to begin playback of the recording. If the recording hasn't been preloaded then it tries to load it, and then starts the playback.


NOTE: If you want to synchronize asciinema player's playback with other elements on the page (for example <audio> element) then you should wait for the play event to occur, which signifies actual start of the playback.


pause method pauses playback.



loadedmetadata, loadeddata, canplay, canplaythrough

The loadedmetadata, loadeddata, canplay and canplaythrough events are fired (all of them, in this order) when the recording has been loaded and is ready to play. The recordings are always fully fetched (you can't partially load JSON) so there's no difference in the amount of metadata/data available between these 4 events - when either event occurs the player already has all the information for smooth playback. In other words, it's enough to listen to only one of them, e.g. canplaythrough (all 4 are supported to make it more in line with HTMLVideoElement).

document.getElementById('player').addEventListener('loadedmetadata', function(e) {
  console.log("duration is", this.duration);

document.getElementById('player').addEventListener('canplaythrough', function(e) {
  console.log("all ready to play");

NOTE: The player starts fetching the recording either when preload attribute is set (in this case these events may not be immediately followed by play event), or when user starts the playback (in this case these events are immediately followed by play event).


The play event is fired when playback has begun.

document.getElementById('player').addEventListener('play', function(e) {
  console.log("it's playing");
  console.log("we're at", this.currentTime);


The pause event is fired when playback has been paused.

document.getElementById('player').addEventListener('pause', function(e) {
  console.log("it's paused");

Keyboard shortcuts

The following keyboard shortcuts are currently available (when the player element is focused):

  • space - play / pause
  • f - toggle fullscreen mode
  • / - rewind 5 seconds / fast-forward 5 seconds
  • 0, 1, 2 ... 9 - jump to 0%, 10%, 20% ... 90%
  • < / > - decrease / increase playback speed


The project uses leiningen for development and build related tasks so make sure you have it installed (as well as Java 7 or 8).

Start local web server with auto-compilation and live code reloading in the browser:

lein figwheel dev

Start auto-compilation of .less files:

lein less auto

Once the above tasks are running, open localhost:3449 in the browser to load the player with sample asciicast. Any changes made to .cljs or .less files will be automatically pushed to the browser, preserving player's state.

Run tests with:

lein doo phantom test

Building from source

To build stand-alone .js and .css files run:

lein cljsbuild once release
lein less once

This produces resources/public/js/asciinema-player.js and resources/public/css/asciinema-player.css.


If you want to contribute to this project check out Contributing page.


Developed with passion by Marcin Kulik and great open source contributors.


Copyright © 2011-2016 Marcin Kulik.

All code is licensed under the GPL, v3 or later. See LICENSE file for details.