# TTFB: definition

> TTFB, or Time To First Byte, measures the delay between the browser sending a request and receiving the first byte of the server's response.

- Source canonique : [https://allaux.fr/en/glossaire/ttfb](https://allaux.fr/en/glossaire/ttfb)
- Langue : EN
- Dernière mise à jour : 2026-09-30

## What TTFB actually measures

TTFB covers everything that happens before the browser receives any page data at all: DNS resolution, connection setup, and above all the time the server takes to process the request, query the database and generate the HTML. It says nothing about the weight of images, CSS or JavaScript, which only come into play after that first byte.

On a PrestaShop or WooCommerce store, a high TTFB almost always points to a server-side problem rather than a front-end one: slow database queries, undersized hosting, a poorly configured application cache, or too many modules running on every page load. Optimising images or minifying JavaScript will have no effect on this figure.

This is an important distinction when diagnosing performance: before tackling image weight, an abnormally high TTFB should point the investigation towards the server, the database or the cache.

## FAQ

### What counts as a good TTFB for an online store?

Under 200 to 300 milliseconds is generally considered good. Above one second, it's almost always a sign of a server or database problem that needs fixing as a priority.

### Does a low TTFB guarantee a fast site for the visitor?

No, it only guarantees that the server responds quickly. The rest of the load, images, scripts, CSS, can still slow down the final render despite an excellent TTFB.

### How can you measure a store's TTFB?

Performance testing tools such as PageSpeed Insights, or the network tools built into browsers, show this delay separately from the page's full load time.