Essence - free minimal and focused log viewer for macOS

macOS 14+, universal .app in .dmg archive

notarized, sandboxed, entitlements: outgoing connections (for lenses 'fetchSync'), user selected file read/write for yaml import/export

Features

• Native, lightweight (~5 MB) & Free
• Token highlighting
• Minimap
  • gutter
  • content preview
  • time of day visualization
• Lenses - tooltips for tokens with Javascript logic
  • get local date from UTC
  • call external system to get user name from user id
  • etc.
• Issue panel with filtering
• Import/export lenses and profiles to yaml
  • Feel free to contribute your own profiles and lenses!

Installation

1. Download dmg archive (from releases on the right side of this page)
2. Mount the dmg and move .app file to /Applications
3. Run the app

Update to a new version: simply grab the newest dmg from Releases and replace your existing .app file in /Applications folder. Your existing profiles and lenses will be preserved.

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Docs

Regex format

The tool works with Apple's NSRegularExpression which is functionally identical to PCRE (Perl Compatible Regular Expressions) for 99% of common use cases. To test your regex, use site like regex101.com and set flavor to PCRE2 or Python.

Profiles and token rules

Profile aggregates one or more token rules. Token rules specify which parts of the text will be highlighted, whether they will be visible in minimap and shown in the issue panel.

Examples

• regex to extract ERROR, SEVERE or FATAL words:

  \b(ERROR|SEVERE|FATAL)\b
  

• regex to extract UTC date:

  \d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2},\d{3}[+-]\d{4}
  

Lenses

Lenses (smart tooltips) can execute logic (defined in Javascript) for the provided token.

Following items are injected into the JS context:

• match - the token the lens is being executed for
• fetchSync - function for making http requests, takes request options object with fields:
  • method - HTTP method, e.g. "GET"
  • headers - key/value pairs

The lense below calls external service to get vendor name based on the MAC address:

Regex for token:

([0-9a-fA-F]{2}[:-]){5}([0-9a-fA-F]{2})

Code:

let requestOptions = {
    method: "GET"
};

// 'fetchSync' and 'match' are provided by Essence app to make a call for the given token
let responseText = fetchSync(`https://api.macvendors.com/` + match, requestOptions);

return responseText;

More Examples

• convert UTC to local time

  let date = new Date(match.replace(',', '.')); // Adjusting string to standard JS format
  if (isNaN(date.getTime())) {
      return "Parsing date...";
  }
  // Return local time string
  return date.toLocaleString();
  

• call external service

  • Please be aware that you are responsible for what data you send to external services.

  let url = "https://xyz.com/rest/api/";
  
  let requestOptions = {
      method: "GET",
      headers: {
          "Accept": "application/json",
          "Authorization": "Basic <BASE64 encoded creds>" 
      }
  };
  
  // 'fetchSync' and 'match' are provided by Essence app to make a call for the given token
  let responseText = fetchSync(url, requestOptions);
  
  // Parse the JSON string
  let responseJson = JSON.parse(responseText);
  
  //parsing logic
  
  return 'something'