Container Images and CI

## One command, two different installs `npx playwright install` downloads **browser builds** — the Chromium, Firefox and WebKit binaries pinned to your installed `@playwright/test` version — into Playwright's browser cache. That is a plain file download; it needs network access and disk, nothing more. Those binaries then have to *link*. On Linux a browser is a dynamically linked executable that needs graphics, font, audio and X/GTK libraries present on the host. A stock CI runner or a slim base image usually has few of them. `npx playwright install --with-deps` adds that second install: it runs the system package manager to put those shared libraries in place, then downloads the browsers. `npx playwright install-deps` is the same OS-package half on its own, for when the browsers are already present but the libraries are not. ## What the deps half needs - **Elevated privileges.** It shells out to the system package manager, so it needs root or `sudo`; an unprivileged CI user gets a permission failure, not a silent skip. - **A supported distro.** The dependency lists Playwright ships target Debian/Ubuntu-family images. On anything else you install the libraries yourself. - **Network to the distro mirrors**, not just to the browser CDN — two different egress paths, which matters on a locked-down runner. - **Time on every run** unless you bake it into an image, because packages installed into a throwaway runner die with the runner. ## Failure modes it prevents Without the OS packages, `npx playwright install` looks like it worked and the failure arrives later, at launch, as a browser process that exits immediately or a message naming a missing `.so` file. That is the confusing shape: the download step is green, the test step dies. `--with-deps` collapses both halves into one step that fails loudly at setup time. | Situation | What to run | Why | |---|---|---| | Bare Ubuntu CI runner, root available | `npx playwright install --with-deps` | Neither browsers nor libraries are present | | Inside `mcr.microsoft.com/playwright:v1.63.0-noble` | nothing | Browsers and libraries already ship in the image | | Slim custom image, browsers cached in a volume | `npx playwright install-deps` | Only the OS libraries are missing | | Local developer laptop | `npx playwright install` | The desktop OS already has the libraries | ## Narrowing what you download Both forms take browser names, so a payroll regression suite that only ever runs Chromium can do `npx playwright install --with-deps chromium` and skip two engines' worth of download and disk. That is usually the single biggest cut to a cold CI setup step. Add engines back when a project in the config actually needs them — installing less than the config launches just moves the failure to launch time. ## Where it fits in a job 1. Check out the repository and install npm dependencies as usual; this step does **not** fetch browsers for you. 2. Run `npx playwright install --with-deps` (optionally naming browsers) as an explicit step. 3. Run the suite. Inside the official image, step 2 disappears, which is most of the reason to use the image at all. Running `--with-deps` there anyway is harmless but wasteful: it re-checks packages that were baked in at build time, adding a slow apt round-trip to every job for no change in outcome. One last point worth saying out loud in an interview: the flag installs **operating-system** dependencies, not npm ones. It has nothing to do with `package.json`, lockfiles, or which browsers your config declares — it is the bridge between a downloaded binary and a Linux box that can actually execute it.