I built this tool for myself. I was hanging a shelf one evening and realised I'd left my physical spirit level at a friend's place. I grabbed my phone, searched for an online alternative, and found nothing that just worked — everything either wanted me to download an app or was buried behind ads and sign-up flows.
So I built one. Spirit Level Online is a free, browser-based bubble level that runs entirely on your phone's built-in sensors. No app needed, no account, no nonsense. Open the page, grant sensor access, and you're levelling.
The tool uses your device's accelerometer to measure tilt in real time and shows it as a traditional bubble level on screen. There are two modes: Surface Mode for flat surfaces like shelves and tables, and Wall Mode for vertical checks like picture frames and TV mounts. It works on any modern smartphone or tablet — iOS and Android.
I've also added audio feedback (a beep that quickens as the bubble approaches centre), a Zero button to calibrate against camera bumps, and dark mode for working in dim spaces. It's available in English, Spanish, German, Italian, French, and Portuguese.
I'm a solo developer. I also built Online Inclinometer for measuring slopes and What Is My Altitude for checking elevation — both the same idea: useful tools that work instantly in your browser.
Your sensor data never leaves your device. All measurements happen locally in your browser — nothing is transmitted to any server. I use GoatCounter to count anonymous page visits (no cookies, no personal data). The site also shows Google AdSense ads, which may use cookies for personalisation — see the Privacy Policy for details.
Questions or bug reports? Get in touch.