Extract Log Levels

Extract log level names such as INFO, WARN and ERROR from log lines.

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^ · $
Start/end; m = lines.
[abc] · \d
Listed character / digit.
* · + · ?
Zero or more, one or more, optional.
(...)
Capture a numbered group.
(?<name>...)
Named capture.
(?=...)
Ahead; lookbehind varies.
i · m · s
Ignore case / line anchors / dot-newline.
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Verified Fixture FX-R02

What it does

Extract the level names INFO, WARN and ERROR from log lines; group 1 is the level.

How to use it

  1. Load the example or paste your log.
  2. Check which lines matched.
  3. Export the levels as a column.

Verified example

Example

Text "level=INFO ready\nlevel=WARN slow"

JavaScript · This browser
\blevel=(INFO|WARN|ERROR)\b

Result: "level=INFO", "level=WARN"

Python re · Local WASM
\blevel=(INFO|WARN|ERROR)\b

Result: "level=INFO", "level=WARN"

PCRE2-8 · Local WASM
\blevel=(INFO|WARN|ERROR)\b

Result: "level=INFO", "level=WARN"

Go regexp · Local WASM
\blevel=(INFO|WARN|ERROR)\b

Result: "level=INFO", "level=WARN"

Counterexample

Text "level=DEBUG"

JavaScript · This browser
\blevel=(INFO|WARN|ERROR)\b

Result: no match

Python re · Local WASM
\blevel=(INFO|WARN|ERROR)\b

Result: no match

PCRE2-8 · Local WASM
\blevel=(INFO|WARN|ERROR)\b

Result: no match

Go regexp · Local WASM
\blevel=(INFO|WARN|ERROR)\b

Result: no match

Recorded by running fixture FX-R02 on : rp.js@1 on Node v24.21.0 (V8), v24.21.0, CPython 3.14.2 (Pyodide 314.0.7), PCRE2 10.48, go1.27.1. JavaScript results come from the rp.js@1 core on Node’s V8; your browser runs the same core.

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