cPanel updates itself. What you control is how soon a new version reaches your server, and whether the operating system underneath keeps patching on its own.
In WHM, Server Configuration → Update Preferences.
The tiers, in one line each
Stable. A version arrives here only after it has been running widely elsewhere. This is where production servers with customers belong.
Release. One step earlier. Newer features, correspondingly less time in the field.
Current and Edge. Progressively earlier still, intended for servers you can afford to break.
The honest framing is that the tier is a trade between features you may not need and surprises you definitely do not want. On a server with paying customers, Stable is the answer unless something specific requires otherwise.
The setting to leave alone
Separately from the tier, WHM offers automatic security updates for the operating system's packages. Leave it on.
People turn it off after one update changed something inconvenient, and then the server sits on unpatched libraries for a year. Those are not comparable risks. The tier choice manages how adventurous your panel is; this setting manages whether known vulnerabilities get fixed at all.
What an update actually interrupts
Less than people expect.
The panel itself is briefly unavailable, WHM and cPanel logins fail for a few minutes during the update. Websites keep serving throughout, because the web server and PHP are not restarted for a routine panel update.
Where interruption does occur is a major version change that rebuilds parts of the stack, or an EasyApache run triggered alongside it. That is a different operation with different timing. For that, see EasyApache and managing PHP versions server-wide.
Major versions deserve five minutes of reading
Minor updates are routine. Major ones occasionally move an interface, deprecate a PHP version, or change a default.
The change log is published before the version reaches Stable, which is the entire benefit of sitting on Stable: you get time to read it. The specific things worth scanning for are removed PHP versions, because that is what silently breaks customer sites, and changes to feature lists, because that is what changes what customers see.
When an update appears to break a site
Check whether the site is actually broken or the panel simply looks different. A large share of post-update tickets are interface changes reported as faults.
Where a real fault exists, it is most often a PHP version that is no longer available, leaving accounts on it falling back to a default they were never tested against. MultiPHP Manager covers checking which version an account is really running, and the answer can differ from what MultiPHP reports if the account is using PHP Selector.
Update timing
WHM runs its update overnight by default. That is usually right, and it is worth confirming the scheduled window is overnight in your server's time zone rather than someone else's.
If you would rather control it, updates can be set to manual, but manual means you now own the job. An update setting switched to manual and then forgotten is worse than either option chosen deliberately.
Tweak Settings worth changing walks through the other server-wide defaults in the same part of WHM, and service status and server health walks through confirming everything came back up afterwards.
Read where you are before deciding anything
The tier is a setting; the version is a fact, and they are not always consistent with each other.
/usr/local/cpanel/cpanel -V cat /etc/cpupdate.conf tail -20 /var/log/cpanel-install.log
The first prints the running version. The second shows the configured tier and whether automatic updates are enabled for the panel and for the operating system separately; two settings people assume are one.
A machine several versions behind on a tier that should be current is the finding worth chasing: it means updates have been failing instead of being declined, and the install log says why.
When an update fails halfway
A failed panel update is not neutral. It can leave services stopped, a package partially replaced, or the panel running with mismatched components.
grep -iE 'error|fatal|failed' /var/log/cpanel-install.log | tail -20 whmapi1 servicestatus 2>/dev/null | grep -A2 'not running'
Read the log before re-running anything. The common causes are unglamorous. The disk filled during the update, a third-party repository conflicted, or a customised configuration file could not be replaced.
Free the space or resolve the conflict first, then run the update again. Repeating it without addressing the cause reproduces the same failure and extends the window in which the machine is in a half-updated state.
PHP is a different update track
The panel updating does not update the PHP versions it manages, and the two are frequently confused because both appear under the same interface.
whmapi1 php_get_installed_versions 2>/dev/null | grep -i 'ea-php' ls /opt/cpanel/ | grep ea-php
A version that has reached end of life keeps working and stops receiving fixes, and the panel will not remove it for you, sites keep running on it indefinitely.
Retiring one is a customer conversation instead of a maintenance task, because it changes what their code runs on. Start it well before the version disappears from the panel's own repositories, which is the point at which the decision stops being yours. There is more on the mechanics in EasyApache and managing PHP versions.
The operating system sets the real deadline
Panel versions come and go on a schedule you can mostly ignore. The operating system underneath does not.
Each major panel release supports a list of operating systems, and a machine on one that has dropped off that list stops receiving panel updates entirely, while appearing perfectly current, because there is nothing newer available for it.
That is not something a tier setting can fix. It is a migration, it takes planning, and the time to start is when the support end date is announced rather than when updates stop arriving. Transferring cPanel accounts between servers deals with the move it eventually requires.