LCP
The LCP page of RUM Monitoring shows how long real visitors wait for the main content, which phase is slow and which element loads last.
The LCP page of RUM Monitoring shows how long your real visitors wait until the main content of a page is on screen. It also shows which phase of the load is slow and which element and files cause the wait.
What LCP means
LCP (Largest Contentful Paint) is how long visitors wait until the main content of the page is on screen. The main content is the largest image, video or block of text in the visible part of the page. LCP is one of Google's three Core Web Vitals.
A slow LCP makes the page feel slow, even when other parts load fast. Visitors can leave before they see your content.
LCP thresholds
| Band | LCP value |
|---|---|
| Good | 2.5 s or less |
| Needs improvement | 4 s or less |
| Poor | More than 4 s |
The headline value is the value of a typical visit: 3 out of 4 page loads were this fast or faster. Google passes LCP when at least 75% of visits are Good. See Metrics and thresholds.
Before you start
- RUM Monitoring needs the RUM script on your pages. See Install the RUM script.
- In the sidebar, open Web performance > RUM Monitoring > LCP.
- Select Phone or Desktop in the filter dock. Every card on the LCP page shows the selected device only.
You can also filter by date, URL Path, Country and Browser, and compare with an earlier period. See Filters and the device.
The LCP verdict
The verdict is one sentence at the top of the LCP page. It shows only when it says something new:
- "On Phone, LCP fails" when the typical LCP is not Good. If the value is only a little over the limit, it adds "Just over the limit."
- "On Phone, LCP passes but is close to the limit" when the typical LCP is Good, but within 10% of 2.5 s.
- "On Phone, LCP got 20% slower" or "got 20% better" when compare is on and LCP changed by 15% or more.
The verdict needs 30 visits or more. If LCP passes with room to spare, the LCP page shows no verdict.
Site Health Monitoring banner
If Site Health Monitoring found issues or opportunities about the Core Web Vitals of the selected device, a banner shows their number. Click Open in Site Health Monitoring to see them. See Site Health Monitoring.
Largest Contentful Paint card
The Largest Contentful Paint on Phone card (or on Desktop) has two tiles and one chart. Click a tile to show its chart.
- Largest Contentful Paint: the typical LCP in the period, colored by its band.
- Good visits: the share of visits with a Good LCP. The tile is green at 75% or more, orange at 50% or more, and red below 50%.
A tile from fewer than 30 visits is gray, with a note such as Only 12 visits. A tile without data shows Not measured for this period.
The LCP chart
For Largest Contentful Paint, the chart shows the typical LCP over time. Two lines mark the Good limit (2.5 s) and the Poor limit (4 s). With compare on, a dashed line shows the earlier period.
For Good visits, the chart shows the share of Good, Needs improvement and Poor visits over time, stacked to 100%. A line marks Passes at 75%, where Google passes LCP.
Use the Hour, Day, Week or Month control to group the chart. A note on a day of the chart tells you that VitalSentinel changed what RUM Monitoring measures, or calculated stored data again, on that day.
Google and your own visitors
The Google and your own visitors card compares your LCP with the LCP that Google publishes for your site. It has four tiles:
| Tile | What it covers |
|---|---|
| Google, Phone and Google, Desktop | Chrome visits to the whole site, last 28 days |
| Your visitors, Phone and Your visitors, Desktop | All visits in the selected period and filters |
Google rates your site from Chrome visits only. RUM Monitoring measures all of your visitors, so the two can differ. A big gap means that Chrome users have a different experience than other visitors.
Click Open CrUX Monitoring to see Google's data. If Google has not published data for your site, the card says "Google has not published data for this site yet". Google reports a site only when it has enough Chrome visits. See CrUX Monitoring.
If CrUX Monitoring is not set up for the domain, the card shows Set up CrUX Monitoring instead. A tile without a figure says "Google has not published enough visits for this device yet." or "Too few visits measured this yet."
Where it is slow
The Where it is slow card lists your pages for the selected device. By default, the pages with the most visits that were not Good come first.
| Column | What it shows |
|---|---|
| Page | The page address. The menu opens the page in other modules. |
| Visits | The visits to the page in the period |
| Google clicks | The clicks from Google web search, from Google Search Console |
| LCP | The typical LCP of the page, with its change when compare is on |
| Good visits | The share of visits with a Good LCP |
| Visits affected | The visits on the page that had an LCP above the Good limit |
Click a header to sort. A page with fewer than 30 visits shows a dash in LCP. Owners and admins can click Watch in Page Monitoring on a row. Start with the first page in the list: it costs the most visits.
Countries
The Countries card shows a world map for the selected device. Each country has the color of its typical LCP: Good, Needs improvement or Poor. Low sample means too few visits to rate, and No data means no visits.
Hover a country to see its visits, its figures, the change from the earlier period and the visits affected. A slow country can point to a long distance to your server. A CDN (content delivery network) can help.
Where the time goes
The Where the time goes on Phone card (or on Desktop) splits LCP into four phases. The chart shows the average time in each phase over time, stacked. The four phases add up to the total LCP.
| Phase | What it is |
|---|---|
| Time to first byte | How long your server takes to begin its answer. Nothing can load before this. |
| Resource load delay | The wait before the largest image or text starts to download |
| Resource load duration | How long the largest image or text takes to download |
| Element render delay | The gap after the download before the largest element shows |
Hover a point to see each phase and the total. With compare on, a line shows the total of the earlier period. If one phase has no reading for a point, the chart shows a gap. Its tooltip says: "Not measured – a phase has no reading, so the total would be too low."
Shorten the longest phase first.
The largest element
The The largest element on Phone card (or on Desktop) shows which kind of element is the largest on your pages. It groups the elements in these kinds:
- Image
- Heading
- Background (a background image)
- General Content (all other elements, for example a block of text)
- N/A (the browser did not report the element)
For each kind, the card shows the share of visits and the typical LCP, colored by its band. Hover a bar to see the visits. The typical LCP of a kind is an average over the tags in the group, weighted by visits.
Make the largest element load first. For example, if it is an image, do not load it lazily.
LCP resource URLs
The LCP resource URLs card lists the images and files behind your largest element, the most frequent first. It shows the selected device only.
| Column | What it shows |
|---|---|
| Resource URL | The full address of the image or file |
| Count | How many visits had this file as the largest element |
| LCP | The typical LCP of those visits, with its change when compare is on |
The table shows 20 files on each page of results. If your largest element is text, such as a heading or a paragraph, the card is empty: "No resource data available".
Compress or resize the slowest file. You can also move it to a faster server.
How to improve LCP
Use the Where the time goes card to find the slow phase, then act on it:
- Time to first byte is long: make your server faster. Use caching and a CDN. See TTFB.
- Resource load delay is long: the browser finds the main image late. Put the image in the HTML, and preload it.
- Resource load duration is long: the file is too large. Compress the image, use a modern format and serve the correct size.
- Element render delay is long: scripts or styles block the display. Remove or delay scripts and styles that the first screen does not need.
Troubleshooting
Why is the LCP resource URLs card empty?
If the largest element on your pages is text, such as a heading or a paragraph, there is no file to show. The card then says "No resource data available". This is normal.
Why does the LCP page say "No Largest Contentful Paint data for this period"?
There were no visits on the selected device in these dates and filters. Select the other device in the dock, select a longer date range, or remove a filter.
Why does the Where the time goes chart have gaps?
If one of the four phases has no reading for a point, the total would be too low. So the chart leaves a gap at that point instead.
Why is my LCP different from the LCP that Google shows?
Google measures Chrome visits to the whole site over 28 days. RUM Monitoring measures all visitors in your selected dates and filters. Compare the two in the Google and your own visitors card.
Related
- Overview - all Core Web Vitals, filters and page-view limits
- TTFB - the first phase of LCP, in detail
- FCP - when the first text or image shows
- Page Views - the LCP phases and element of one visit
- Metrics and thresholds - the limits of every metric
- CrUX Monitoring - Google's own LCP for your site
