Merge Request Preview Environments

Applies to: FlexLab

Overview

Merge Request Preview Environments (often shortened to MRE or “preview envs”) spin up a temporary copy of your site for a single GitLab merge request (MR). Stakeholders can click a preview link to review changes before they merge to production.

Key concepts

  • Merge request — a proposal to combine one branch into another, with discussion and code review in GitLab.
  • Preview URL — a short-lived hostname FlexSite assigns to the MR build.
  • Teardown — when the MR closes or merges, FlexSite removes the preview to save credits.

Prerequisites

  • FlexLab project with MRE enabled in the platform template or org settings.
  • A .gitlab-ci.yml job that creates preview environments (included in standard FlexSite templates).

Steps

  1. Push a feature branch and open a merge request in GitLab.
  2. Wait for the pipeline’s preview job to finish.
  3. Find the preview link in the MR comment, GitLab Environments tab, or a temporary card on FlexSite Environments.
  4. Share the URL with reviewers; test acceptance criteria on real infrastructure.
  5. Merge or close the MR — the preview environment is destroyed automatically.

Credits and cleanup

Preview environments spend credits while running. Close stale merge requests you no longer need.

MRE is FlexLab only — Codeless and Atom do not use Git merge requests.