How it works
The Log Viewer parses and displays structured log files — JSON logs (one object per line), Apache/Nginx access logs, syslog format, and plain text logs — with filtering, search, syntax highlighting, and severity level color coding. Upload a log file or paste log lines and navigate them in a readable interface.
Log files are typically viewed in terminal scrollback, which lacks filtering and highlighting. Log management tools (Datadog, Splunk, CloudWatch) are powerful but require the log to be shipped to a server — a privacy concern for sensitive application logs containing user data, API keys, or personally identifiable information. This browser-based viewer lets you read and search logs locally.
How to use it: upload a log file or paste log text. The tool auto-detects the format. Log entries are parsed and displayed with timestamp, severity (INFO, WARN, ERROR, DEBUG), source, and message. Use the filter bar to search by keyword, severity level, or time range. Click any entry to expand its full details (for JSON logs, nested fields are shown as a formatted tree).
Formats supported: plain text (one line = one entry), JSON Lines (NDJSON), Apache Combined Log Format, Nginx access log, syslog RFC 5424, Docker log JSON format.
Severity color coding: DEBUG (gray), INFO (green), WARN (yellow), ERROR (red), FATAL/CRITICAL (dark red) — instantly scans to the errors without reading line by line.
Privacy: your log file is processed entirely in the browser. Log content containing API keys, user data, or internal system details is never transmitted.
Frequently Asked Questions
- Plain text (one line = one entry), JSON Lines / NDJSON (one JSON object per line), Apache Combined Log Format, Nginx access log format, syslog RFC 5424, Docker JSON log format ({log, stream, time}), and Log4j/Log4j2 pattern layouts (configurable pattern string).
- Yes. Use the filter bar to set multiple conditions: severity = ERROR AND timestamp > 2024-01-15T10:00 AND message contains 'timeout'. Multiple filter conditions are combined with AND logic. Clear individual conditions with the × button.
- Files up to ~100MB load smoothly in most browsers using streaming text parsing. Files between 100–500MB may be slow on first load but still work. Files over 500MB may exceed browser memory limits — for very large log files, use a dedicated log analysis tool like jq, grep, or an ELK stack.
- Application logs frequently contain sensitive data: user IDs, session tokens, internal API keys, database query parameters, and IP addresses. Uploading these to a third-party log viewer means your sensitive data leaves your environment. This viewer processes logs entirely in your browser — no log line is ever transmitted.