Log Formatter

The Log Formatter is a client-side tool that parses, reformats, and filters log output from applications, servers, and CI/CD pipelines. It accepts raw log text — typically a wall of unstructured lines from stdout or a log file — and transforms it into a readable, organized format. The tool offers three output modes, each designed for a different analysis task. In Structured mode, it normalizes log level tags (INFO, WARN, ERROR, DEBUG, TRACE, FATAL) into a consistent padded format like [ERROR ] or [INFO ], strips common timestamp prefixes that vary between logging frameworks (e.g., [12345.678] from Node.js), and produces clean, aligned output. In Timeline mode, it extracts ISO 8601 or common timestamp formats from each line and arranges the output chronologically with aligned timestamps and level tags, making it easy to trace the sequence of events. In Errors Only mode, it filters the log to show only lines containing ERROR, ERR, FATAL, SEVERE, FAIL, Exception, Traceback, or panic — cutting through thousands of lines to surface the information you actually need when debugging. The tool also produces a summary of log level counts (e.g., "ERROR: 12, WARN: 34, INFO: 1200") displayed in the info bar, giving you an instant overview of the log's health without reading every line. All processing happens locally in the browser with no server calls.

Developers spend significant time reading logs, but raw log output is rarely consistent. Different services, frameworks, and environments produce logs with different formats: some prefix timestamps as [2024-01-15T10:30:00.000Z], others as [10:30:00], others as Jan 15 10:30:00. Log levels appear as INFO, info, [INFO], or just the absence of a tag. When debugging an issue, you often need to quickly answer: how many errors occurred? What happened right before the failure? What was the timeline of events? The Log Formatter answers these questions instantly. Errors Only mode is especially valuable when triaging production incidents — instead of scrolling through 10,000 lines of health-check pings and debug traces, you see only the 15 error lines that matter. Timeline mode is invaluable when correlating events across multiple services or understanding the sequence of operations in a distributed system. The structured alignment mode makes side-by-side comparison of log files trivial, since every level tag occupies the same column width.

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.

What log formats does the formatter support?

<p>The formatter is designed to be format-agnostic: it looks for common patterns (level keywords like INFO/ERROR, ISO timestamps, bracket-prefixed levels) and applies them when found. It works with logs from Node.js, Python, Java, Go, nginx, systemd, and most other standard logging frameworks.</p>

Is there a line count limit?

<p>There is no hard line limit. The formatter processes all input lines in memory. Extremely large logs (millions of lines) may cause brief browser pauses depending on your device's available memory.</p>

Can I use this for structured JSON logs?

<p>The formatter is designed for plain-text log lines. For JSON-formatted logs (e.g., from pino or winston in JSON mode), the JSON Formatter tool would be more appropriate. However, the Errors Only mode can still filter JSON logs by searching for error-level keywords in the raw text.</p>

Does the timeline mode sort the lines?

<p>In Timeline mode, the formatter extracts timestamps from each line and displays them in a column but preserves the original line order — it does not re-sort the lines. This is intentional: log lines are typically already in chronological order from the source, and re-sorting could mask issues related to out-of-order delivery in distributed systems.</p>