---
url: /reference/formats.md
description: The on-disk formats a Recording serializes to — .tape, .cast, and .tty/.ttyz.
---

# Recording Formats

A [Recording](../../concepts/recording) is one concept; these are the three
on-disk **formats** it serializes to and from. A format is an *encoding* — not a
domain object.

| Format                  | Role                                               | Tracks it carries                            |
| ----------------------- | -------------------------------------------------- | -------------------------------------------- |
| [`.tape`](./tape)       | charm/VHS interop — a *compiler* input             | commands                                     |
| [`.cast`](./asciicast)  | asciinema interop — a symmetric *codec*            | io                                           |
| [`.tty`/`.ttyz`](./tty) | termless native — live bundle dir ⇄ sealed archive | commands + io + frames + facts + checkpoints |

Use `.tape` to author a session by hand or interop with VHS. Use `.cast` to
interop with the asciinema ecosystem. Use `.tty`/`.ttyz` for termless's own lossless,
all-tracks form.