Short answer: not via an environment variable. In Prefect 3.x (and 2.x), there isn’t a supported env var or setting to change the browser tab title of the UI. The UI settings exposed today cover enabling the UI, API URL, and base path—not title/branding. What you can do (self‑hosted only): - Override the UI’s static files and edit the HTML title tag. 1) Copy the Prefect UI static assets from your environment to a custom directory (e.g., /opt/prefect-ui). 2) Edit index.html and change the <title>…</title>. 3) Point Prefect to your custom static directory and start the server:

export PREFECT_UI_STATIC_DIRECTORY=/opt/prefect-ui
prefect server start

Notes: - This is an advanced/unsupported customization; future Prefect upgrades may require you to rebase your modified index.html against newer UI assets. - Prefect Cloud’s UI is managed and does not expose branding or title customization. References: - Prefect 3 settings reference - ServerUISettings API - Self-hosting guide If you’re on Cloud or need a different kind of branding, let me know your setup (Cloud vs. self‑hosted and Prefect version) and what you’re aiming to change exactly—I can suggest the safest path.