Best Free Colony Counter Websites (2026)

Colony Counter (colony-counter.net) is our top pick for a free colony counter website in 2026. It was built specifically for microbiologists who need to count agar plates without installing software or creating an account. Upload a petri dish photo, let the tool detect colonies automatically, fine-tune the count by adding or removing marks, and convert the result to CFU/mL — all in one browser tab. Because it runs entirely in the browser, it works equally well on a lab PC and on the phone you used to photograph the plate.

Lab Laps (lablaps.com) earns the #2 spot because it bridges online colony counting with a much wider bench workflow — completely free. On the web, you can upload an agar plate or petri dish photo and run AI detection without logging in — then review and adjust boxes before confirming your count. The Lab Laps mobile app goes further: colony counting sits alongside protocol management, multiple labelled timers, cell culture routines, serial dilution calculators, buffer prep, and plate labelling. For labs that treat counting as one step in a longer experiment — not an isolated task — Lab Laps is the strongest integrated option after a dedicated counter site.

Colonia is best known as a mobile AI colony counting app, but its website outlines the same photo-based detection approach: snap a plate, get an automatic count in seconds. Processing happens on-device in the apps, which appeals to labs with strict data-handling rules. We include it here because many researchers discover it while searching for online tools, even though the deepest experience is on iOS and Android rather than in a desktop browser.

Prompt2Tool's colony counter is a privacy-friendly option because processing stays in your browser, but it ranks lower than dedicated tools. It lives on a broad calculator website rather than a microbiology-focused product, so the workflow feels generic and the UI offers minimal help for plate-counting conventions. Sensitivity sliders and overlays are useful, yet accuracy can drop on harder plates, and there is no CFU/mL step. Fine for a quick private count if you already use the site, but most labs will get a smoother experience from the options ranked above.

Online-Colony-Counter.com lands last on our list. The free pixel-based counter technically works on desktop, but the experience lags behind what microbiologists expect in 2026: the design is dated and cluttered, the workflow is slow, and the site pushes users toward a paid AI tier for features that top free tools already offer without a subscription. Mobile support is effectively absent on the free version, and there is no integrated CFU calculator. It may suffice if you already know the tool and work exclusively from a bench PC, but for most labs there are faster, better-designed free options above.