This error usually means the system-level Cairo library is missing or not detected during Pycairo installation. Even if it worked before, system updates or environment changes might have removed or altered it.

To fix it, ensure Cairo is installed on your system: on Ubuntu/Debian, run sudo apt install libcairo2-dev, or on macOS with Homebrew, run brew install cairo.

Then try reinstalling Pycairo using pip install pycairo.

Thank you for your reply. However, I am currently using Railway's online service, where I push my code to GitHub and deploy to Railway from GitHub. I have tried to create nixpacks.toml, and add this:

[phases.setup]

aptPkgs = [

"libcairo2-dev",

"pkg-config",

"python3-dev"

]

But this doesn't work. I have tried to use both Railpack and Nixpack, but got the same error.

Pycairo needs system-level Cairo libraries, and just adding them in nixpacks.toml may not be enough. On Railway, you should explicitly list all required build dependencies. try this in your nixpacks.toml

[phases.setup]
aptPkgs = [
  "libcairo2-dev",
  "pkg-config",
  "python3-dev",
  "libgirepository1.0-dev",
  "libglib2.0-dev"
]

Then push and redeploy.

Thank you for the follow-up. I have tried your method, but it doesn't work. I still got the same error message. I have reviewed the discussions, and it appears that someone has encountered the same issue. pycairo no longer installs - Railway Help Station

I think maybe this is a problem with the Railway, because I was able to deploy several days ago, and now I can also deploy if I remove cairo from my requirements. I am not sure if they can solve it or not, but I am moving my code to Azure for stability.

Replace pycairo with cairocffi (pure Python alternative)
If your code doesn’t depend on very deep Cairo internals, you can swap cairocffi.

It’s API-compatible in most cases and doesn’t require system Cairo libs. But if u still want pycairo then Use a custom Dockerfile build instead of Nixpacks.