# Lagless vs Preroll

> Two Mac apps that lower AirPlay audio delay using the same macOS setting. How they differ in approval, controls and extras, and when to pick each.

Updated 2026-10-06. Canonical page: https://lagless.app/vs/lagless-vs-preroll/

> Lagless and Preroll both lower macOS's AirPlay buffer with the `audioLatencyMs` setting, and both keep the stream awake with inaudible noise. Preroll discovered and documented the mechanism and applies it with a standard admin prompt. Lagless uses a helper you approve once, adds presets, per-speaker memory and an undo, and lives in the menu bar.

## At a glance

| | Preroll | Lagless |
|---|---|---|
| Mechanism | `audioLatencyMs`, root's preferences | Same |
| Keep-alive noise | Yes, −78 dBFS | Yes, −78 dBFS, AirPlay only |
| Changing the value | Admin prompt per change | One-time helper approval |
| Lowest value offered | Slider with manual entry | 350 ms (lower is silent) |
| Presets | – | Responsive, Balanced, Safe |
| Shows the speaker's live delay | – | Yes, before and after |
| Per-speaker memory | – | Yes |
| Price and licence | Free, MIT | Free, MIT |

Details of Preroll are from its [README](https://github.com/ksha23/preroll) and [notes](https://github.com/ksha23/preroll/blob/main/NOTES.md); check them for its current features.

## Credit where it's due

Preroll found the setting, worked out that only root's preferences are read, measured the 250 ms floor and designed the keep-alive. Lagless builds on that research.

## Which to choose

- **Pick Preroll** if you want the original, prefer an admin prompt per change, or want its optional per-speaker switching helper.
- **Pick Lagless** if you want a menu bar app with presets, a live readout and no prompt after setup.

## Sources

- [Preroll README](https://github.com/ksha23/preroll)
- [Preroll research notes](https://github.com/ksha23/preroll/blob/main/NOTES.md)