Log file viewer that opens large .log files in your browser, even multi-GB ones. Filter by level, text, regex or time and jump between errors. No upload.
Also known as: log file viewer · log viewer online · large log file viewer · open log file online · online log viewer free · json log viewer online · log analyzer online · view log file in browser · filter log file by level · big log file reader
Log file viewer that opens large .log files in your browser, even multi-GB ones. Filter by level, text, regex or time and jump between errors. No upload.
Is Log File Viewer free to use?
Yes. Log File Viewer is completely free with no usage limits, and there is no paid tier required to use it.
Do I need an account to use Log File Viewer?
No. Log File Viewer works immediately in your browser with no signup, login, or email address required.
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Drop a .log or .log.gz file here, or click to browse
Multi-GB files are indexed in 4 MB slices and never uploaded.
Log Entries
1INFO
2INFO
3WARN
4ERROR+6
11INFO
Every entry in the log will appear here with its line number and level. Stack traces stay grouped with the line that logged them, and the level, text, regex and time filters narrow millions of lines in seconds.
About Log File Viewer
A log file viewer is used to open, search and filter log files that are too large or too noisy for a text editor. Drop in an nginx, Apache, application, syslog or JSON log, even a multi-gigabyte one, then filter by level, text, regular expression or time, keep stack traces grouped with the line that logged them, and jump from error to error. The file is read in your browser and never uploaded.
Key Features
Opens multi-gigabyte .log files and gzip-compressed rotated logs (.log.gz) by indexing them 4 MB at a time, so only the rows on screen are decoded
Detects levels and timestamps in nginx, Apache, syslog, journald, Docker, Kubernetes klog, logcat, Spring Boot, log4j, Python logging, pino, Serilog and other JSON lines
Keeps Java, Python, Go, .NET and PHP stack traces grouped with the log line that produced them instead of scattering frames across the view
Filters by level, plain text, regular expression and time range, then jumps to the previous or next error; access-log lines take their level from the status code
Groups errors into signatures by masking numbers, hex, UUIDs and IP addresses, so one failure repeated 4,000 times shows up as one line with a count
Saves the filtered lines as a new .log file and copies a text report with level counts, time span and the top error signatures
Use Cases
Finding the 502s in an nginx access log pulled from an EC2 instance in us-east-1 after a Black Friday traffic spike
Reading a 2 GB catalina.out from a Tomcat server that VS Code and Notepad++ refuse to open
Seeing which exception a Spring Boot service threw 4,000 times overnight before the 9:00 AM ET standup
Narrowing a kubectl logs dump to the WARN and ERROR entries between 2:00 and 2:15 AM during an incident review
Checking a customer's support bundle (.log.gz) for errors without uploading it to a third-party service, which matters under SOC 2 and HIPAA
Supported Formats
.log, .txt, .out and files with no extension, such as syslog or messages
nginx, Apache, IIS (W3C), CloudFront and AWS ALB access logs
Syslog (RFC 3164 and 5424), journalctl, klog, Android logcat
UTF-8, UTF-16 and Windows-1252 text
Related Keywords
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How do I open a log file that is too big for Notepad or VS Code?
Editors load the whole file into memory and lay out every line, so a log past a few hundred megabytes freezes them or refuses to open. On a server you would reach for less, tail or grep. This viewer works more like less: it reads the file in 4 MB slices, keeps about 21 bytes of index per entry, and decodes only the rows on screen. In Chrome on an M3 Pro MacBook Pro, a 1 GB test log with 8.4 million entries indexed in 6 to 8 seconds, and a full-text search over it took 3 to 4 seconds. Rotated .gz logs open directly. An entry matches a search when its own text does, stack trace included, and times are compared as written in the file.
Your log never leaves this tab
The file is read with the browser's File API and indexed in memory. Nothing is uploaded, and auto-save keeps only the text report (level counts, time span, top error signatures) and pasted snippets under 200 KB, never an opened file.