GitHub - mrtoadie/go-check-cert: simple validity checker for website certificates with web dashboard

Stay secure, stay informed

Cert-Checker is a privacy-focused Go tool that monitors SSL/TLS certificates on domains and local files, analyzes expiration dates, and alerts users if any issues are detected. It offers both a powerful command-line interface for automation and an interactive web dashboard.

Features

Certificate Verification
- Hybrid Scanning: Supports remote domains (https://example.com) and local certificate files (.pem, .crt, .key).
- Chain Validation: Verifies certificate chains, detects self-signed certificates, and identifies missing intermediates.
- CI/CD Ready: Returns specific exit codes (0=OK, 1=Warning, 2=Error) for integration into pipelines.
Interactive Web Dashboard
- Real-Time Visualization: Responsive UI with Dark Mode support.
- Filtering: Filter by status, search by domain/issuer, and sort by expiration date.
- Auto-Refresh: Configurable background updates (e.g., every 15 mins) to keep data fresh.
Security & Privacy
- Local Storage: No external databases or cloud dependencies required.
- HTTPS Dashboard: Built-in support for self-signed or Let's Encrypt certificates to secure the dashboard connection.
Automation & Management
- Cron Job Manager: Built-in interactive CLI to create, list, and remove scheduled scans.
- Reporting: Exports detailed JSON reports with timestamps for archival or external processing.
- Save Certificates: Download valid certificates (optional)

Quick Start

Build from source

git clone https://github.com/mrtoadie/go-check-cert.git
cd go-check-cert
go build -o cert-checker

Run directly (without build)

Arch Linux

Install from AUR

Launch with Dashboard

# Without HTTPS
./cert-checker -web

# With HTTPS and self-signed certificate
./cert-checker -web -cert ./certs/cert.pem -key ./certs/key.pem

Open http://localhost:8080 or https://localhost:8080 in your browser.

Screenshots

Command Line Options

Flag	Alias	Description
-f	-file	Path to a local .pem, .crt, .cer, or .key file
-c	-cron	Interactive Cron setup
-dl	-download	Download valid certificates to certs folder
-ls	-list	List and manage Cron jobs
-l	-log	Show cron job log file
-ci	-ci-mode	CI/CD Mode (non-interactive, uses urls.txt)
-w	-web	Start web dashboard on localhost:8080
-cert		Path to SSL certificate file (.pem/.crt)
-key		Path to SSL private key file (.pem)
-h	-help	Display help message

Examples

Check a single certificate:

./cert-checker -f ./server.crt

Set up cron job(s):

List active Cron jobs:

Configuration

The tool automatically creates a configuration file on the first run.

Location: ~/.config/cert-checker/urls.txt

Format: One URL per line. Comments starting with # are supported.

Output Examples

Text Output (Default)

=== RESULTS ===

1. forum.linuxguides.de
   Days:  44 | Valid: 26.02.26 → 27.05.26
   Issuer: R12
------------------------------------
2. github.com
   Days:  52 | Valid: 06.03.26 → 03.06.26
   Issuer: Sectigo Public Server Authentication CA DV E36
------------------------------------
=== SUMMARY ===
OK: 0 | Warn: 2 | Exp: 0 | Err: 0

JSON Output

{
  "generated_at": "2026-05-03T14:47:42Z",
  "total_count": 1,
  "results": [
    {
      "url": "https://github.com",
      "status": "OK",
      "days_remaining": 180,
      "is_chain_complete": true,
      "key_algorithm": "RSA",
      "key_size": 2048
    }
  ]
}

Cron Job Management

Interactive Menu

Options:

Set up cron job – Create a new automated check
List & manage jobs – View/delete existing jobs
Exit – Quit the program

List Cron Jobs

./cert-checker -list
``

Output:
```bash
=== CERTIFICATE CHECK CRON JOBS ===

1. # cert-checker - 2026-05-03 14:47:42
   0 8 * * * /home/user/cert-checker -ci >> /tmp/cert-check.log 2>&1

2. # cert-checker - 2026-05-03 15:00:00
   0 */6 * * * /home/user/cert-checker -ci >> /tmp/cert-check.log 2>&1

Total: 2 job(s) found.

Delete Individual Jobs

Run ./cert-checker -list
Select "Delete individual jobs"
Mark jobs with Spacebar
Confirm with Enter

Usage

The input is interactive and automatically detects the correct format.

Press Enter to use the default list of URLs (~/.config/cert-checker/urls.txt)
To check individual URLs: github.com or github.com, ubuntu.com, example.org
Check local certificate file: '~/github.pem'
Certificate files can also be checked using a flag: cert-checker --file ~/github.pem

Certificate files with the following extensions work: .pem, .cer, .crt, .key

Tested on

✅ Arch Linux

✅ Solus

✅ WSL2 (Ubuntu)

License

go-check-cert is licensed under the MIT License.