Log filter & field extractor

Filter log lines by a literal substring, then optionally extract a named JSON field or a whitespace-delimited column.

01 Input

YOUR INPUT

02 Output

LOCAL RESULT

QUICK GUIDE / 28

How to use

Select Load example to restore the sample, or replace the labeled inputs with your own values.
Review the options and select Run tool. No input is sent to a server.
Filtering is literal and case-sensitive. JSON field mode reads one direct property, not a dot-separated path. For Whitespace column mode, set the last field to a column number such as 2. An empty Contains field matches every nonblank line. Extracting an empty JSON string produces an empty, copyable result.
Inspect the result, then copy or download it. Clear removes visible inputs and output.

A worked example

Load example restores these values.

Log lines:
{"level":"info","message":"started"}
{"level":"error","message":"failed"}

Contains (case-sensitive):
error

Output:
Full lines

Field name or column number (starts at 1):
message

Expected result

The full-lines result contains only {"level":"error","message":"failed"}. JSON field mode with message returns failed.

Scope & limitations

Only matching lines are parsed. Missing fields and malformed matching records are errors. No regex execution or streaming of large files. JSON numbers use JavaScript binary64 precision; keep large exact identifiers as strings. Numeric overflow is rejected.

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Log filter & field extractor

01 Input

02 Output

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