# Best speed (with preset dictionary) — file signature 78 7D at offset 0

For Best speed (with preset dictionary), hex signature is 78 7D; offset is 0; extension is zlib, verified against its source on 2026-09-22.

- **Hex signature:** 78 7D _(verified: appears in the quote below)_
- **Offset:** 0 _(verified: appears in the quote below)_
- **Extension:** zlib _(verified: appears in the quote below)_
- **Format:** Best speed (with preset dictionary) _(verified: appears in the quote below)_

## What the source says

> 78 01 | x␁ | 0 | zlib | No Compression (no preset dictionary) | 78 5E | x^ | Best speed (no preset dictionary) | 78 9C | xœ | Default Compression (no preset dictionary) | 78 DA | xÚ | Best Compression (no preset dictionary) | 78 20 | x␠ | No Compression (with preset dictionary) | 78 7D | x} | Best speed (with preset dictionary) |

## Source

- https://en.wikipedia.org/wiki/List_of_file_signatures

Last verified: 2026-09-22. Review by: 2027-09-22.
Part of [File format magic numbers](https://referencesource.org/file-format-signatures/).