Awesome Open Source
Awesome Open Source


Log viewer which translates JSON logs into pretty human-readable representation. It is a faster alternative to humanlog and hlogf with several additional features.

Installation options

  • Download latest release from download page

  • Download and extract using curl and tar on Linux

    curl -sSfL | tar xz
  • Download and extract using curl and tar on macOS

    curl -sSfL | tar xz




Features and usage

Concatenation of multiple log files

  • Concatenate all log files


    $ hl $(ls -tr /var/log/example/*.log)

    Concatenates and humanizes all *.log files found in /var/log/example/.

Support for gzipped log files

  • Concatenate all log files including gzipped log files


    $ hl $(ls -tr /var/log/example/*.{log,log.gz})

    Concatenates and humanizes all *.log and *.log.gz files found in /var/log/example/.

Automatic usage of pager

  • Use default pager with default parameters


    $ hl example.log

    Automatically opens less pager with default parameters.

  • Override options for default pager


    $ LESS=-SR hl example.log

    Opens less pager with disabled line wrapping.

  • Use custom pager


    $ PAGER=bat hl example.log

    Opens bat pager.

Quick filtering by log level

  • Errors only


    $ hl -l e

    Shows only messages with error log level.

  • Errors and warnings


    $ hl -l w

    Shows only messages with warning and error log level.

  • Errors, warnings and informational


    $ hl -l i

    Shows all log messages except debug level messages.

Using live log streaming

  • Command

    $ tail -f example.log | hl -P

    Follows changes in example.log file and displays them immediately. Flag -P disables automatic using of pager in this case.

Filtering by field values

  • Command

    $ hl example.log -f component=tsdb

    Shows only messages with field component having value tsdb.

  • Command

    $ hl example.log -f component!=tsdb -f component!=uninteresting

    Shows only messages with field component having value other than tsdb or uninteresting.

  • Command

    $ hl example.log -f provider~=string

    Shows only messages with field provider containing sub-string string.

Filtering by time range

  • Command

    $ hl example.log --since 'Jun 19 11:22:33' --until yesterday

    Shows only messages occurred after Jun 19 11:22:33 UTC of the current year (or of the previous one if current date is less than Jun 19 11:22:33) and until yesterday midnight.

  • Command

    $ hl example.log --since -3d

    Shows only messages for the last 72 hours.

  • Command

    $ hl example.log --until '2021-06-01 18:00:00' --local

    Shows only messages occurred before 6 PM on 1st Jun 2021 in local time as well as show timestamps in local time.

Hiding or showing selected fields

  • Command

    $ hl example.log --hide provider

    Hides field provider.

  • Command

    $ hl example.log --show provider

    Hides all fields except provider.

  • Command

    $ hl example.log -h headers -h body -H headers.content-type

    Hides fields headers and body but shows a single sub-field content-type inside field headers.

Configuration files

  • Configuration file is loaded automatically if found at predefined platform-specific location.

    OS Location
    macOS ~/.config/hl/config.yaml
    Linux ~/.config/hl/config.yaml
    Windows %USERPROFILE%\AppData\Roaming\hl\config.yaml
  • Any parameters in the configuration file are optional and may be omitted. In this case default values will be used.

Default configuration file

Envrionment variables

  • Many parameters which are defined in command-line arguments and configuration files may be specified by envrionment variables also.

Precedence of configuraton sources

  • Configuration file
  • Environment variables
  • Command-line arguments


  • HL_TIME_FORMAT='%y-%m-%d %T.%3N' overrides time format specified in configuration file.
  • HL_TIME_ZONE=Europe/Moscow overrides time zone specified in configuration file.
  • HL_CONCURRENCY=4 overrides concurrency limit specified in configuration file.
  • HL_PAGING=never specified default value for paging option but it may be overriden by command-line arguments.


Stock themes

Selecting current theme

  • Using theme value in the configuration file.
  • Using environment variable, i.e. HL_THEME=classic, overrides the value specified in configuration file.
  • Using command-line argument, i.e. --theme classic, overrides all other values.

Custom themes

  • Custom themes are loaded automatically if found at predefined platform-specific location.

    OS Location
    macOS ~/.config/hl/themes/*.yaml
    Linux ~/.config/hl/themes/*.yaml
    Windows %USERPROFILE%\AppData\Roaming\hl\themes*.yaml
  • Format description

    • Section elements contains styles for predefined elements.
    • Section levels contains optional overrides for styles defined in elements sections per logging level, which are [debug, info, warning, error].
    • Each element style contains optional background, foreground and modes parameters.
    • Example
              foreground: <color>
              background: <color>
              modes: [<mode>, <mode>, ...]
                  foreground: <color>
                  background: <color>
                  modes: [<mode>, <mode>, ...]
    • Color format is one of
      • Keyword default specifies default color defined by the terminal.
      • ASCII basic color name, one of
        • black
        • red
        • green
        • yellow
        • blue
        • magenta
        • cyan
        • white
        • bright-black
        • bright-red
        • bright-green
        • bright-yellow
        • bright-blue
        • bright-magenta
        • bright-cyan
        • bright-white
      • 256-color palette code, from 0 to 255.
      • RGB color in hex web color format, i.e. #FFFF00 for bright yellow color.
    • Modes is a list of additional styles, each of them is one of
      • bold
      • faint
      • italic
      • underline
      • slow-blink
      • rapid-blink
      • reverse
      • conseal
      • crossed-out

Complete set of options and flags

hl 0.10.3
JSON log converter to human readable representation

    hl [FLAGS] [OPTIONS] [--] [FILE]...

    -c                   Handful alias for --color=always, overrides --color option
        --help           Prints help information
        --list-themes    List available themes and exit
    -L, --local          Use local time zone, overrides --time-zone option
    -P                   Handful alias for --paging=never, overrides --paging option
    -r, --raw-fields     Disable unescaping and prettifying of field values
    -V, --version        Prints version information

        --buffer-size <buffer-size>                          Buffer size [env: HL_BUFFER_SIZE=]  [default: 2 MiB]
        --color <color>                                      Color output options, one of { auto, always, never } [env: HL_COLOR=]  [default: auto]
    -C, --concurrency <concurrency>                          Number of processing threads [env: HL_CONCURRENCY=]
    -f, --filter <filter>...                                 Filtering by field values in one of forms [<key>=<value>, <key>~=<value>, <key>~~=<value>, <key>!=<value>, <key>!~=<value>, <key>!~~=<value>] where ~ denotes substring match and ~~ denotes regular expression match
    -h, --hide <hide>...                                     Hide fields with the specified keys
    -e, --hide-empty-fields <hide-empty-fields>              Hide empty fields, applies for null, string, object and array fields only [env: HL_HIDE_EMPTY_FIELDS=]
        --interrupt-ignore-count <interrupt-ignore-count>    Number of interrupts to ignore, i.e. Ctrl-C (SIGINT) [env: HL_INTERRUPT_IGNORE_COUNT=]  [default: 3]
    -l, --level <level>                                      Filtering by level, one of { d[ebug], i[nfo], w[arning], e[rror] } [env: HL_LEVEL=]
        --max-message-size <max-message-size>                Maximum message size [env: HL_MAX_MESSAGE_SIZE=]  [default: 64 MiB]
        --paging <paging>                                    Output paging options, one of { auto, always, never } [env: HL_PAGING=]  [default: auto]
    -H, --show <show>...                                     Hide all fields except fields with the specified keys
    -E, --show-empty-fields <show-empty-fields>              Show empty fields, overrides --hide-empty-fields option [env: HL_SHOW_EMPTY_FIELDS=]
        --since <since>                                      Filtering by timestamp >= the value (--time-zone and --local options are honored)
        --theme <theme>                                      Color theme [env: HL_THEME=]  [default: one-dark-green]
    -t, --time-format <time-format>                          Time format, see [env: HL_TIME_FORMAT=]  [default: %b %d %T.%3N]
    -Z, --time-zone <time-zone>                              Time zone name, see column "TZ database name" at [env: HL_TIME_ZONE=]  [default: UTC]
    -u, --unhide <unhide>...                                 Unhide fields with the specified keys
        --until <until>                                      Filtering by timestamp <= the value (--time-zone and --local options are honored)

    <FILE>...    Files to process


  • MacBook Pro (16-inch, 2019)
    • CPU - 2,4 GHz 8-Core Intel Core i9
    • OS - macOS 10.15.6
    • Data - ~1GiB log file, 4.150.000 lines
      • hl v0.6.8 ~ 1 second
        $ time hl prom-m2.log -c >/dev/null
        hl prom-m2.log -c > /dev/null  12.41s user 0.64s system 1430% cpu 0.912 total
      • hlogf v1.4.1 ~ 10 seconds
        $ time hlogf prom-m2.log --color= >/dev/null
        hlogf prom-m2.log --color= > /dev/null  9.91s user 1.22s system 101% cpu 10.970 total
      • humanlog v0.4.1 ~ 60 seconds
        $ time humanlog <prom-m2.log >/dev/null
        humanlog> reading stdin...
        humanlog < prom-m2.log > /dev/null  58.55s user 4.89s system 107% cpu 58.931 total
      performance chart

Future features

  • Optional sorting of log messages by timestamp

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