[BUG] Steam overlay BrowserView rejects `file://` URLs — "BrowserView.Create initial URL not valid"

[joyearnaud]

System information

• Steam client version (build): 1782533657 (≈ 2026-06-24, non-flatpak native install at ~/.local/share/Steam)
• Distribution: Bazzite 44.20260629.0 (Fedora Silverblue 44 base, rpm-ostree immutable)
• Kernel: 7.0.9-ogc3.2.fc44.x86_64
• GPU: NVIDIA GeForce RTX 4070 SUPER, driver 610.43.02 (akmods build)
• Opted into Steam client beta: No
• SteamUI error reference: Shared SteamUI_10776939_ed33390ce6a94616

Please describe your issue

Games that open local HTML content (manuals/wikis/encyclopedias) via file:// URLs in the Steam overlay fail completely. The overlay shows a blank/grey screen and the client logs:

Error Reference: Shared SteamUI_10776939_ed33390ce6a94616
BrowserView.Create initial URL not valid.

Concrete example: Total War: ROME REMASTERED (Feral Interactive port, appid 885970). The game's in-game wiki/encyclopedia is opened through the Steam overlay browser. The game constructs a URL of the form:

file:///var/home/<user>/.../Total War ROME REMASTERED/share/data/manual/en/index.html

and passes it to the Steam overlay (BrowserView/CEF), which rejects it outright with the error above. The wiki is completely unusable in-game (alt+click on encyclopedia entries → grey overlay). The file exists and is valid (opens fine in a normal external browser via xdg-open).

Steps to reproduce

1. Launch Total War: ROME REMASTERED (any game that opens a local file:// URL in the overlay should reproduce).
2. Start a campaign, then alt+click on any wiki/encyclopedia entry (e.g. a unit, building, or the help button).
3. The Steam overlay opens but shows a blank/grey screen.
4. Check Steam logs → BrowserView.Create initial URL not valid / Shared SteamUI_10776939_....

Expected: the local HTML page loads in the overlay browser.
Actual: URL rejected as "not valid" → blank overlay.

This is a regression

In issue #6208 (2021), Valve engineer @kisak-valve confirmed that file:///path/to/file (three consecutive slashes, absolute path) worked correctly in both the Big Picture overlay and the desktop overlay:

"I copied the url to some local nVidia driver docs to Steam's overlay and it opened fine with both the big picture overlay and the desktop mode overlay... you need to give a full absolute path to the local file, so it'll end up looking like file:///path/to/file."

The newer BrowserView API (current Steam client) now rejects the same file:/// scheme as an invalid initial URL. Functionality that previously worked is broken.

Notes / what would help

• Re-allow the file:///file:/// scheme as a valid initial URL for BrowserView.Create (as it was in 2021), OR
• Document the intended scheme for local content so porters (Feral, etc.) can migrate their in-game browsers away from file://.

A user-side workaround is to open the same index.html in an external browser — but this defeats the in-game alt+click integration, which cannot be redirected (the URL is constructed internally by the game binary and is not moddable).

Related

• [Future Request] add support local (file://) address default page #6208 — [Future Request] add support local (file://) address default page (open; previously confirmed working in 2021)
• Fails to open URLs (affects in-game links) #11779 — Fails to open URLs (affects in-game links) (open)

Workaround (for affected users)

Open the local manual in an external browser instead of the overlay:

xdg-open "/path/to/game/.../manual/en/index.html"

This is the only currently working path on Linux; the in-game overlay integration stays broken until file:// is re-accepted by BrowserView.