You can use the auto_update_core parameter when creating/updating profiles in order to specify if your browser profiles will update automatically as soon as new cores are released. It can be used in the Start Quick Profile, Profile Create, Profile Update, and Profile Partial Update endpoints. 

• Enable automatic updates (default): If auto_update_core is true, the profile will automatically update to the latest core version

"auto_update_core": true,

• Disable automatic updates: Set auto_update_core to false and specify the required core_version

"core_version": 154,
"auto_update_core": false,

Consider the following while using this feature:

• If you want to keep your current core version, you must ensure that the auto_update_core flag is set to false, preventing it from being automatically updated
• When updating a profile, changing the core version to anything other than the latest version is not supported
• We recommend keeping automatic core updates enabled unless your workflow specifically requires a supported fixed core version. Newer cores include current compatibility and browser updates
• Our servers usually provide latest 6 versions. If you want to use an even older version – you will not be able to do so. Let's say, the latest version of Mimic is 154. In that case, the oldest possible version is 149
• For minor versions you can use core_minor_version parameter. It sets a specific minor version of the selected browser core, for example 154.1, 154.2. The version must be currently available.

Which setting should I use?

Use automatic updates: keep auto_update_core set to true when you want the profile to move to the latest supported core automatically.

Keep a fixed core: set auto_update_core to false and use a supported core_version.

Check available versions: use Load Browser Core endpoint before setting a specific core version.