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.
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.
Frequently asked questions
What counts as a good TTFB for an online store?
Does a low TTFB guarantee a fast site for the visitor?
How can you measure a store's TTFB?
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