Time to First Byte (TTFB) measures how long it takes for your server to start responding after a visitor requests a page. While not a Core Web Vital itself, TTFB directly affects LCP, your page can't display content until the server starts sending data.
TTFB thresholds
Rating | Score | What it means |
Good | ≤ 800ms | Server responds quickly |
Needs Improvement | 800ms – 1800ms | Noticeable delay before page starts loading |
Poor | > 1800ms | Server response is too slow |
How TTFB affects LCP
TTFB is the starting point for everything else. If your TTFB is 1 second, your LCP cannot be faster than 1 second and will likely be higher once you add resource loading and rendering time.
When diagnosing slow LCP, check TTFB first. If TTFB is poor, improving it will directly improve LCP.
Understanding the TTFB detail page
The TTFB detail page shows:
P75 score card: Your 75th percentile TTFB
TTFB distribution: Histogram showing the spread of response times
TTFB timeline: Score over time with comparison to the previous period
TTFB rating over time: Daily breakdown of Good/Needs Improvement/Poor
TTFB by country: Geographic performance (expect variation based on distance from CDN servers)
Top and poorest pages: Identify which pages have the slowest server response
What you can influence on Shopify
Since Shopify manages your hosting, you can't control server configuration directly. However, you can reduce server processing time by:
Removing unused apps — each app may add processing overhead
Simplifying Liquid templates — complex loops and conditionals take longer to render server-side
Note: Some TTFB variation is expected, especially for visitors far from CDN edge servers or during high-traffic periods. Focus on keeping your theme and apps lean rather than expecting dramatic improvements.
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