Build Queues

Build queueing is when a build must wait for resources to become available before starting. This creates more time between when the code is committed and the deployment being ready.

• With On-Demand Concurrent Builds, builds will never queue.
• Without On-Demand Concurrent Builds, builds can queue under the conditions specified below.

On-Demand Concurrent Builds prevent build queueing so your team can build faster. Vercel dynamically scales the amount of builds that can run simultaneously.

You can choose between two modes:

• Run all builds immediately: All builds proceed in parallel without waiting. Your builds will never be queued.
• Run up to one build per branch: Limit to one active build per branch. New deployments to the same branch won't be processed while there is an ongoing build, but builds to different branches proceed immediately.

To configure on-demand concurrent builds, see Project-level on-demand concurrent builds.

If you're experiencing build queues, we strongly recommend enabling On-Demand Concurrent Builds. For billing information, see Pricing.

When multiple deployments are started concurrently from code changes, Vercel's build system places deployments into one of the following queues:

• Concurrency queue: The basics of build resource management
• Git branch queue: How builds to the same branch are managed

This queue manages how many builds can run in parallel based on the number of concurrent build slots available to the team. If all concurrent build slots are in use, new builds are queued until a slot becomes available unless you have On-Demand Concurrent Builds enabled at the project level.

Concurrent build slots are the key factor in concurrent build queuing. They control how many builds can run at the same time and ensure efficient use of resources while prioritizing the latest changes.

Each account plan includes a number of build slots that apply only when On-Demand Concurrent Builds is disabled:

• Hobby accounts allow one build at a time.
• Pro accounts include 3 concurrent build slots by default. The first build slot is included, and standard build minutes within it are not billed.
• Enterprise accounts can have custom limits based on their plan.

Builds are handled sequentially. If new commits are pushed while a build is in progress:

1. The current build is completed first.
2. Queued builds for earlier commits are skipped.
3. The most recent commit is built and deployed.

This means that commits in between the current build and most recent commit will not produce builds.