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Lighthouse doesn't wait long enough for page to load (NO_LCP)

See original GitHub issue

Steps to reproduce

Run lighthouse https://clientes-bancocaminos.grupocaminos.es
Open report

What is the current behavior?

On CLI I get: largest-contentful-paint:warn Caught exception: NO_LCP

On DevTools I get: Largest Contentful Paint Error! Something went wrong with recording the trace over your page load. Please run Lighthouse again. (NO_LCP)

What is the expected behavior?

I don’t expect any errors.

Environment Information

Affected Channels: CLI, DevTools
Lighthouse version: 6.1.1
Chrome version: 84.0.4147.105

Issue Analytics

State:
Created 3 years ago
Comments:10 (3 by maintainers)

Top GitHub Comments

1reaction

patrickhulcecommented, Sep 2, 2020

Would adding a _waitForLcp make _waitForFcp redundant?

From the technical page load perspective yes but lighthouse treats FCP specially so we’ll probably still want both for two main reasons.

We want the thresholds for each to be very different (FCP on order of ~15s whereas LCP should be close to maxWaitForLoad)
Failure of FCP means the entire run fails whereas LCP missing only fails a few audits.

1reaction

patrickhulcecommented, Jul 29, 2020

Ah thanks for the example report, in that case it looks like Lighthouse did not wait long enough for the page to completely finish. You can control this from the CLI with the networkQuietThresholdMs in a custom config, but we should try to wait long enough for LCP at least too.