Hugo ignores a setting in hugo.toml

You add a setting to hugo.toml. You restart the server. Nothing changes. No error, no warning – Hugo builds happily and behaves as if the line isn’t there.

Look at where the line sits:

baseURL = "https://example.com/"
title = "My site"

[params]
  author = "Anders"
  description = "A site"

theme = "papermod"

theme is at the bottom, at the left margin, unindented. It looks top-level. It isn’t.

Why

TOML has no braces. A [section] header opens a table, and every key after it belongs to that table until the next header. Indentation is decoration; TOML doesn’t read it.

So Hugo doesn’t see theme. It sees params.theme – a parameter called “theme” that nothing reads. Which is a perfectly valid thing to write, so nobody complains. The site just builds without your theme.

The same trap catches every top-level key: baseURL, title, languageCode, ignoreLogs, enableGitInfo, disableKinds. Anything you append to the end of a config file that has sections in it.

The fix

Move the key above the first [section] header:

baseURL = "https://example.com/"
title = "My site"
theme = "papermod"

[params]
  author = "Anders"
  description = "A site"

Rule of thumb: top-level keys go at the top of the file. Once the first [table] header appears, the top level is over.

How to tell it’s happening

Ask Hugo what it thinks the config is:

hugo config

That prints the resolved configuration. If theme shows up as an empty string while the word “theme” is clearly in your file, you’ve found it – the key is somewhere Hugo isn’t looking.

YAML has the same problem, differently

In YAML, indentation is the structure, so the failure looks like this:

baseURL: https://example.com/
params:
  author: Anders
  theme: papermod     # ← two spaces in, so it's params.theme

Same result: a parameter nobody reads. Move it back to the left margin.

Empty sections are harmless – but they hide things

A [section] header with nothing under it does nothing at all. It’s still worth deleting: an empty header is usually the ghost of a key that got moved, and the next key you add at the bottom of the file will land under it.

HugoKit checks this before every publish, without waiting for the build to fail – there’s nothing to fail. It knows roughly forty keys that belong at the top level, finds the ones stranded under a table header, and offers to move them back, marking each one with # Moved from [params] by HugoKit so you can see what happened. Empty sections get cleaned up in the same pass. Both are shown as a diff you approve. See Editing your config and Preflight.