I have a theory that only bad projects get finished — good ones keep finding new things to do. Asciinema is a case in point. What started as a way to share terminal sessions with friends has, over 14 years, grown into a full suite of tools covering recording, hosting, playback, and live streaming — and been rebuilt multiple times along the way. So what does it actually take to record and replay a terminal session faithfully in a browser?Joining us for this conversation is Marcin Kulik, Asciinema's creator. The project's architecture has passed through almost every interesting corner of software engineering: a Python recorder built around pseudo-terminals (PTY), a ClojureScript terminal emulator for the browser that hit performance limits with immutable data structures and garbage collection pressure, a move to Rust compiled to WebAssembly, a Go experiment that didn't last, and a new Rust CLI for concurrent live streaming backed by an Elixir/Phoenix server that calls Rust code via NIFs. The same Rust terminal emulator library now powers all three components — the browser player, the server, and the CLI.If you've ever looked at those terminal animations embedded in a README and wondered what's underneath them, or if you're interested in how a passionate open-source developer navigates 14 years of language changes and rewrites, this conversation has plenty to offer.---Support Developer Voices on Patreon: https://patreon.com/DeveloperVoicesSupport Developer Voices on YouTube: https://www.youtube.com/@DeveloperVoices/joinAsciinema: https://asciinema.orgAsciinema Docs: https://docs.asciinema.orgAsciinema CLI (GitHub): https://github.com/asciinema/asciinemaAsciinema Player (GitHub): https://github.com/asciinema/asciinema-playerAsciinema Server (GitHub): https://github.com/asciinema/asciinema-serverAVT - Rust terminal emulator library: https://github.com/asciinema/avtvt-clj - the original ClojureScript terminal emulator: https://github.com/asciinema/vt-cljPaul Williams' ANSI/VT100 State Machine Parser: https://vt100.net/emu/dec_ansi_parserRust: https://www.rust-lang.orgWebAssembly: https://webassembly.orgSolidJS: https://www.solidjs.comElixir: https://elixir-lang.orgPhoenix Framework: https://www.phoenixframework.orgRustler (Rust NIFs for Elixir/Erlang): https://github.com/rusterlium/rustlerClojure: https://clojure.orgClojureScript: https://clojurescript.orgcmatrix: https://github.com/abishekvashok/cmatrixMarcin Kulik on GitHub: https://github.com/ku1ikMarcin Kulik on Mastodon: https://hachyderm.io/@ku1ikMarcin Kulik on asciinema.org: https://asciinema.org/~ku1ik"They're Made Out of Meat" demo: https://asciinema.org/a/746358Kris on Bluesky: https://bsky.app/profile/krisajenkins.bsky.socialKris on Mastodon: http://mastodon.social/@krisajenkinsKris on LinkedIn: https://www.linkedin.com/in/krisjenkins/---0:00 Intro2:28 What Is Asciinema?4:48 How Asciinema Started9:51 The Problem of Parsing Terminal Output14:07 Building a Cross-Platform Recorder17:01 Rewriting the Parser in ClojureScript22:19 The Hidden Complexity of Terminals29:28 Rendering Terminals in the Browser39:47 When ClojureScript Can't Keep Up45:28 Moving to Rust and WebAssembly52:01 The Go Experiment57:43 Adding Live Terminal Streaming1:07:12 Can You Scrub Back in a Live Stream?1:14:40 Editing Recordings1:25:27 Outro