By default Gearset will look at your source and target and pick the highest API version that's supported by both.
When getting started with your Devops journey this works well as it gets you going quickly.
As you look to mature your process it's recommended to build a process to understand what API version you should be using and when to update it.
For more information about building the correct process your team I recommend reading the below blog post
Index
What is the latest API version Gearset supports?
Gearset now supports API version 63 (Spring '25). In our app the oldest API version you're able to select is version 37 (Summer '16).
How to check the API version of a Salesforce org?
You can check your Salesforce org's API version by going to Setup > Custom code > Apex Classes > New > Version Settings.
In there, you can check the API version:
If you're interested, Salesforce's Help Centre documentation shows more ways of identifying your current API version: Find Salesforce Edition and API version.
Changing the API version in the Compare and deploy and CI jobs
Occasionally it's useful to be able to override the API version that Gearset has picked. This is done through the metadata filter dialog.
Change the API version in a compare and deploy comparison
Change the API version in a compare and deploy comparison
These steps consider that you have already run your comparison from Compare and deploy page by clicking on the blue Compare now button:
And if you're already on your comparison results page, select the cog 
icon which is a setting to access Manage custom filters:
On the next page, you'll see a menu on the right hand side with a heading Filter options for all types.
On here you can select the dropdown under API version and amend it according to your needs. Once done, select the blue Update comparison button in the bottom right.
This API version will now be used for retrieval from Salesforce, and any deployments that result from the comparison.
Optionally, you can save this selection into a custom filter for re-use later and to share the setting with the rest of your team. For more information on this, see the Custom metadata filters article.
Change the API version in a CI job
Change the API version in a CI job
On the Continuous integration page, open the CI job dashboard to view your CI jobs.
Search for the CI job that you want to use a different API version, then click Edit Settings to adjust the metadata filter.
Then go to the Metadata filter section of the CI job settings, where you can adjust the API version Gearset uses (dropdown under API version on the right hand side).
Once done, select Save CI job.
Note: If you are using a Git branch as a source, you need to update the sfdx.json file mentioned below. This is because only setting the API version in the Gearset metadata filter will not override it.
Changing the API version in your repository (Version control system)
To update the API version in your repository, you need to update the definition file.
If your repository is in SFDX format (Gearset default) it will be sfdx-project.json
If your repository is in MDAPI format this will be package.xml
If these files aren't present, Gearset will try to deduce the version based on the types of metadata in the repository. If Gearset still can't tell, it will default to assuming your metadata is in API version of the current supported default.
Salesforce DX source format repo (Gearset Default)
Salesforce DX source format repo (Gearset Default)
Locate your sfdx-project.json file and change the sourceApiVersion value, as shown in the screenshot below.
Metadata API format repo
Metadata API format repo
Locate your package.xml file and change the version value, as shown in the screenshot below.
How to update the API version used in your pipeline.
How to update the API version used in your pipeline.
Before updating the API version in your pipeline it's highly recommended that you have a process setup to manage when you should update your API version
Please take a look at the below blog to get. abetter understadning of the advantages and posable issues with updating the API version used in your pipeline before continuing.
Once you are ready, you can follow the below steps to update the API version used for your pipeline.
You will need todo this directly from your version control provider as Gearset can not update the API version directly.
1: Create a new feature branch from your Main/Master branch in your VCP, in this case I'm calling it API-update-63
2: Find your config file in the repo and update it with the current API version.
todo this you can follow this guidance at the beginning of this doc.
In this case I'm changing the API version to 63 in Github using the Salesforce DX source format
3: In your pipeline select one of your dev environments and change the selected branch to the new branch you have created.
Then click "create pull request"
4: Deploy this PR down the pipeline like any other PR, after this is committed a new environment that environment will now be using the new API version.
For this reason it's a good idea to run a few other deployments to the environment to test the new API version before pushing all the way to production.
5:Once this reaches production all environments will be updated and using the latest API version.
If you have any questions about API's feel free to reach out in our in-app chat and we are happy to answer any questions you might have