The average time between when a pull request is opened and when it received its first review. Each pull request is counted only once (not as many times as there are reviewers). Time to First Review excludes self-reviews.
Why it matters
This represents the amount of time, on average, that a submitter is left waiting for feedback. When this metric is high, submitters either waste time waiting or are compelled to open up multiple tracks of work. This results in an increase in their team’s work in progress, which, in turn, negatively impacts Cycle Time.
How to use it
If the Time to First Review is elevated, consider setting clearer code review expectations discussing how reviews can better be integrated into engineers' day-to-day routines.
To help set clear expectations for reviewing engineers and to track how often PR reviews take "too long", we recommend setting a target for Decrease pull request time to review. We find that aiming to have 95% of PRs reviewed in 8 business hours provides an achievable target that helps to keep the review process moving quickly.
The median organization averages Time to First Review of 15 hours. The fastest quarter of organizations average less than 10 hours, while the slowest quarter of organizations average more than 23 hours.
What's the difference between Review Speed and Time to First Review?
The similarity between these 2 metrics can be confusing! The difference is found by looking at these questions:
How long does it take a specific person to give their first review on a PR?
How long does it take to get to the very first review on a PR?
Review Speed is a metric that's associated with the reviewer. It represents the time between when a pull request is opened and when a specific reviewer first submits feedback.
If I open a PR and you review it 5 hours later, and Dave reviews it 7 hours later,
you would receive a Review Speed of 5 hours, and
Dave would receive a Review Speed of 7 hours for completing that review.
Time to First Review is a metric associated with a pull request, much like Time to Open and Time to Merge. It represents the time between when a pull request is opened and when the PR received its first review.
If I open a PR and you review it 5 hours later, and Dave reviews it 7 hours later, you would see that the Time to First Review for the PR is 5 hours.
The following metaphor can be helpful:
Review Speed is how long it takes my specific delivery person, on average, to deliver a package. Time to First Review is how long it takes packages to be delivered to my house.
Review Speed is an attribute of a reviewer, as it applies to a given contributor or team to describe their review performance. Time to First Review is an attribute of Pull Requests, as it describes how long PRs sit before receiving a review.
To connect to the analogy, the delivery person is the contributor/team, and the package is the PR (Review Speed is the delivery person’s speed, and Time to First Review is the package’s delivery time).