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Log formats
Colorizing is on by default. Start with --ui-no-colors to turn it off server-wide; each viewer can flip the Colors button in the sidebar, and that per-browser choice is remembered and overrides the server default.
-
Line already has ANSI escape codes (an app using
chalk,colorlog, ...): the codes are rendered as-is and format detection is skipped for that line. A badge in the topbar shows ANSI colors (all selected sources) or Mixed colors (some), and a Sanitized download button appears. - Plain-text line: frontail recognises the format and colors the fields: timestamps, IPs, HTTP methods and paths, status codes (2xx green, 3xx cyan, 4xx amber, 5xx red), thread and pid, log level.
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Nothing matches: a generic fallback still colors timestamps (including
2024/01/01 12:00:00), level words, IPv4 addresses,[bracketed]metadata and"quoted strings".
| Format | Example |
|---|---|
| JSON lines (pino, winston, bunyan, structured logging) |
{"level":"error","msg":"boom"} shown as colorized key=value pairs |
| logfmt | ts=2026-10-10T18:20:10Z level=error msg="db unreachable" |
| Apache / Nginx access log (combined, common, HTTP/1.x/2/3) | 10.0.0.5 - - [10/Oct/2026:18:20:01 +0000] "GET /api HTTP/2.0" 200 5120 |
Apache error log (classic and [core:error]) |
[Fri Oct 10 18:20:01.1 2026] [core:error] [pid 12] ... |
| Nginx error log | 2026/10/10 18:20:01 [error] 12#0: ... |
Tomcat / Catalina (juli, one-line and two-line) |
10-Oct-2026 18:20:01.123 INFO [main] org.apache.catalina... |
| Spring Boot default console | 2026-10-10 18:20:03.123 INFO 4242 --- [main] c.e.App : Started |
Logback / Log4j [thread] LEVEL logger
|
18:20:04.456 [http-1] ERROR c.e.UserService - Failed |
| Log4j / Logback pipe-delimited | 2026-10-10 18:20:04,456 | INFO | message |
Python logging
|
INFO:root:hello and 2026-10-10 18:20:05,789 - worker - WARNING - msg
|
| PostgreSQL | 2026-10-10 18:20:06.001 UTC [1234] ERROR: relation ... |
| MySQL 8 / MariaDB | 2026-10-10T18:20:07.123456Z 0 [Warning] [MY-010068] [Server] ... |
| Kubernetes klog / glog | E1010 18:20:08.123456 1 controller.go:177] failed |
| Redis | 1234:M 10 Oct 2026 18:20:09.123 * Ready to accept connections |
| Java stack traces |
at com.example.Foo.bar(Foo.java:42), Caused by: ..., Exception in thread "main" ...
|
| Python tracebacks |
Traceback (most recent call last): and File "/app/x.py", line 3, in <module>
|
syslog (also what --journal produces) |
Oct 10 18:20:12 myhost sshd[2231]: Accepted publickey ... |
Not seeing your format? Use Custom format rules, or open an issue with a few sample lines.
Taken from the live demo.
| Format | Example |
|---|---|
| Apache / Nginx access log |  |
| JSON lines / logfmt |  |
| Nginx error log |  |
| Apache2 error log |  |
| Tomcat / Catalina |  |
| Log4j / Logback |  |
| syslog |  |
| Generic fallback |  |
If a source contains ANSI codes, a Sanitized download button appears next to Download. It strips the escape sequences line by line on the server (/download?...&sanitize=1), handy for pasting logs elsewhere.
