What the Previews on Windows Terminal Themes Show

The previews on Windows Terminal Themes show how a theme will look in three different contexts before you copy it: a simulated terminal session, an ANSI colour test, and a syntax-highlighted code block. Together they let you judge contrast, readability, and colour balance without installing anything. You switch between them with the Terminal, Colours, and Codeblock selectors at the top of the page, and the preview updates to match whichever theme is currently selected.

The three preview modes

Terminal preview

This mode simulates a real command-line session. The excerpt on the site shows output such as a compiled build, a running test suite, and a local development server address:

CRA - compiled
Cypress - run
Jest - failed
Jest - running
Compiled successfully!
You can now view terminal in the browser.
Local: http://localhost:3000/themes
On Your Network: http://192.168.86.37:3000/themes

Use it to check the things you actually stare at all day: default foreground text on the background, dimmed or secondary output, and success/failure lines. If a theme makes "Jest - failed" and "Compiled successfully!" hard to tell apart at a glance, that is a practical problem, not just an aesthetic one.

Colours test preview

This mode lays out the ANSI colour slots — the standard palette that programs use for red, green, yellow, blue, magenta, cyan, white, and their bright variants, plus black and the background/foreground entries. Because so many CLI tools, prompts, and loggers map their output onto these sixteen slots, this view tells you whether the palette is coherent: whether the bright colours are distinguishable from the normal ones, whether the reds and greens stay readable against the background, and whether any slot is so dark it disappears.

Codeblock preview

This mode shows syntax highlighting colours, so you can see how keywords, strings, comments, and other token types are coloured. This matters if you spend time in editors, git diff, or any tool that colourises source. A theme can look fine in a plain terminal and still produce low-contrast comments or clashing string colours here.

Why the three views matter together

A theme that passes one preview can fail another. A palette with a pleasant background may have a red ANSI slot that is nearly invisible, or syntax colours that were never tuned for that background. Checking all three before copying is the fastest way to avoid pasting a theme, restarting the terminal, and immediately reverting it.

Practical checks before you copy

• Contrast first. Confirm body text is comfortable against the background, not just technically visible.
• Compare similar colours. In the Colours view, check that red and magenta, or blue and cyan, don't blur together.
• Test your worst case. If you read a lot of logs, look at the failure lines in the Terminal preview; if you read code, look at comments in the Codeblock preview.
• Switch themes in place. The theme list (from 3024 Night and Aardvark Blue through to entries like Dracula, GruvboxDark, and Catppuccin variants) lets you move between options while the preview stays open, so you can compare candidates back to back.

Once a theme looks right in all three views, you can copy it and apply it to Windows Terminal. The previews are a screening step, not a guarantee — your own font, font size, and monitor will still affect the final result — but they catch the obvious mismatches before you commit.