Log Analyzer

📖 Tool Introduction

Log Analyzer is a free online tool built for developers and operators. When a production service misbehaves, a log file with tens of thousands of lines is often overwhelming: the ERROR and FATAL lines you actually need are buried under a flood of INFO entries, and the same recurring error repeats over and over. This tool does all parsing locally in your browser: it detects the log level of every line (DEBUG, INFO, WARN, ERROR, FATAL), shows per-level counts and proportion bars in stat cards, lets you tick the levels to keep, and stacks include/exclude keywords on top to strip the noise. More usefully, the Top error signatures feature normalizes timestamps, numbers and hex addresses out of ERROR/FATAL lines, then groups them by message and ranks them by frequency, telling you directly which kind of error happens most often so you can find the root cause instead of reading line by line. The filtered result can be downloaded as a new .log file for forwarding or archiving. All computation happens locally, so logs never reach a server, which makes the analyzer safe for sensitive logs that contain user data, intranet addresses or key fragments. The level detection works on conventional formats that embed the level word in each line, and lines without a recognized level default to INFO so nothing is dropped silently. Because the whole analysis runs on your machine, the tool also works on locked-down intranets and offline laptops, and it never throttles on slow uploads since nothing is transmitted. Whether you triage a crash dump, review a nightly batch run, or hunt for a rare warning that only appears once a day, the filter-and-stats loop turns a wall of text into a short list of actionable signals. A built-in sample loads a realistic mixed log the moment you click the example button, so first-time users can immediately tick levels, toggle keywords and read the top-error panel without locating their own debug file. Because the signature normalizer strips timestamps, counters and hex addresses before grouping, the top panel collapses thousands of slightly different stack lines into a handful of real root causes, which is where most real debugging starts. The downloaded filtered log contains every match rather than the on-screen preview cap, so the file you hand to a teammate or attach to an incident ticket is complete. The whole workflow needs no account, no upload and no installation, which makes the analyzer safe for logs that carry internal URLs, user identifiers or partial stack traces.

✨ Key Features

• Auto level detection: recognizes DEBUG/INFO/WARN/ERROR/FATAL per line
• Level stat cards: counts and proportion bars at a glance
• Keyword filter: include and exclude keywords stack to cut noise
• Top error signatures: normalize timestamps and numbers, group by message
• Result export: download the filtered log as a new file
• Local and safe: logs are parsed in the browser, never uploaded

📝 How to Use

1. Drop the log file into the dashed box, or click to choose it
2. Tick the log levels you want to keep in the filter panel
3. Optionally add include and exclude keywords to narrow further
4. Click Analyze log to see stats, top errors and filtered lines
5. Click Download filtered to export the matching lines as a new log

⚠️ Notes

• Level detection: lines without a level keyword default to INFO
• Case sensitive: level and keyword matching is case-sensitive
• Result cap: the pane shows 500 lines; the download has all matches
• File size: each file is capped near 20MB; split bigger logs
• Privacy: logs never upload, sensitive content is safe