Mine is Playwright.
Free. Open source. Maintained by Microsoft.
It does browser automation, testing, screenshot generation, PDF creation — and it handles dynamic JavaScript pages that Selenium chokes on.
I use it to:
- Monitor competitor websites for price changes
- Generate screenshots of web pages for reports
- Automate form submissions
- Scrape JavaScript-heavy single-page apps
Every time I set it up for a new project, I think "this should cost $50/month."
Runner-ups:
- SQLite — a database in a single file. Powers more apps than any other DB.
- jq — JSON processing in the terminal. Use it 20+ times a day.
- ripgrep — searches 100GB codebases in seconds.
- Apify Free Tier — run web scrapers in the cloud, 5 sec/day free compute.
What's yours? The tool that makes you think "how is this free?"
Bonus points if it's something obscure that most devs haven't heard of.
More from me: 10 Dev Tools I Use Daily | 77 Scrapers on a Schedule | 150+ Free APIs
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