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logseer is a column-based indexing log viewer. It is a cross-platform clone of LogGrok.

Some prominent features:

  • Support for custom column-based log formats.
  • Ability to mark columns as indexed to enable fast filtering.
  • Large files support.
  • Linux and Windows support.
  • Unicode support.

The latest windows binaries are available here.




Building on Fedora

Install the dependencies

$ dnf install git gcc-c++ cmake boost-devel qt5-devel spdlog-devel fmt-devel pcre2-devel

Clone the repository recursively

$ git clone --recurse-submodules

Configure and build

$ mkdir /path/to/build-dir
$ cd /path/to/build-dir
$ cmake /path/to/repo
$ make
$ make install

To cross-compile for windows you need MinGW

$ dnf install mingw64-gcc-c++ mingw64-boost mingw64-qt5-qtbase-devel mingw64-qt5-qtsvg

Now configure and build

$ mingw64-cmake \
    -D CMAKE_CXX_IMPLICIT_INCLUDE_DIRECTORIES="/usr/x86_64-w64-mingw32/sys-root/mingw/include" \
$ make package

General settings

The config is stored in the home directory ~/.logseer/logseer.json. It is created on startup if it doesn't exist.

    "font": {
        "name": "Mono",
        "size": 10
    "general": {
        "maxThreads": 10,
        "showCloseTabButton": true
    "search": {
        "caseSensitive": false,
        "messageOnly": false,
        "regex": false,
        "unicode": false
} is the font name used for the log text.

font.size is the font size in points.

general.maxThreads up to maxThreads threads will be used for indexing. Set to 0 to use all available cores.

general.showCloseTabButton is used to show or hide the Close Tab button on each tab. The Ctrl+W shortcut and the menu entry are unaffected.

search.* are the search settings. They are updated at runtime by logseer.

Regex parsers

It is possible to extend logseer via format description files stored in the ~/.logseer/regex/ directory.

Each file name needs to have the following format <priority>_<name>.json, e.g. 100_simple.json. When logseer opens a log file it tries each json in succession according to its priority, with 0 being the highest priority.

Let's take this simple log as an example

10 INFO CORE message 1
15 INFO SUB message 2
17 WARN CORE message 3
20 INFO SUB message 4
30 ERR CORE message 5
40 WARN SUB message 6


Its format can be described with the following json format specification

    "description": "test description",
    "regex": "(\\d+) (.*?) (.*?) (.*)",
    "columns": [
            "name": "Timestamp",
            "group": 1,
            "indexed": false
            "name": "Level",
            "group": 2,
            "indexed": true
            "name": "Component",
            "group": 3,
            "indexed": true
            "name": "Message",
            "group": 4,
            "indexed": false
    "colors": [
            "column": "Level",
            "value": "ERR",
            "color": "ff0000"
            "column": "Level",
            "value": "WARN",
            "color": "aa0000"

description is the log format description. It is unused for now.

regex specifies a pattern that extracts the columns from a text line. It needs to produce a set of regex groups that will then be treated as columns. There might be unused groups.

magic is the first few characters of the log file, used to select the appropriate log format when opening new files. If not specified, logseer will attempt to parse the first few lines of the log file with different parsers and select the first one that doesn't err.

detector can be specified instead of magic as a log format detector. It's a lua script that is called each time logseer tries to open a log file. The script should return True if it recognizes the log file format. It can base its decision on two global variables:

  • fileName -- log file name.
  • lines -- an array of pairs { string text, boolean parsed }. It contains the first several lines of the log file, with parsed indicating the result of matching text against regex.

Example lua detectors:

"return string.find(fileName, '.ext') ~= nil"
"return #lines >= 2 and lines[0].parsed and lines[1].parsed"
"return #lines >= 2 and lines[0].text == 'A'"

columns is an array that provides descriptions for columns, extracted using the regex property. is the header of the column, as it appears in the UI. is the index of the regex group that provides the value for this column. Indexes start from 1.

columns.indexed is a boolean indicating that the column should allow filtering. It makes sense to mark as indexed columns with a small range of possible values.

colors is an array of predicates that allow changing line colors in the UI. When selecting the line color, logseer evaluates the predicates in order, until the first match (if any).

colors.column is the name of the column for which the color applies.

colors.value is the expected value of the column.

colors.color is an RGB hex value of the color.

Keyboard shortcuts

Key Action
F5 Reload.
Ctrl+1..9 Edit the filter of the corresponding indexed column.
Home Go to the beginning of the log.
End Go to the end of the log.
Ctrl+F Focus the search line (then ENTER to search).
Ctrl+Tab Switch to the next tab.
Ctrl+Shift+Tab Switch to the previous tab.
Ctrl+W Close the current tab.
Ctrl+R Clear all filters.
Ctrl+C Copy selected lines.
Ctrl+G Goto line.
Ctrl+Shift+C Copy selected lines (with headers and spaces).