About DecoLog
DecoLog is a free dive logbook, gas-management toolkit and decompression planner for technical divers — CCR, sidemount, trimix — with full recreational support. It runs in your browser, installs as an app, and keeps working with no signal.
Why it exists
Technical diving software has historically come in two flavours: capable but paid and ageing, or free but shallow. We wanted the tools a tech diver actually plans with — ZHL-16C with gradient factors and VPM-B, real-gas blending, CCR and bailout planning, oxygen-exposure tracking — with none of the usual strings:
- Offline-first. Dive planning happens on boats, in fill stations and at remote sites. Your data lives on your device; the app works with zero connectivity. Cloud sync is optional, not required.
- No subscription. Free, no ads, no paywall around the "pro" features. A logbook you might keep for decades shouldn't be held hostage by a monthly fee.
- Technical-diver focus. Built around the numbers tech divers actually argue about — gradient factors, conservatism levels, END conventions, gas density, rock bottom — while staying simple enough for a first nitrox course.
How we work
Two principles run through everything here. First, show the sources: the algorithms are the published ones — Bühlmann's coefficients, the Yount/Hoffman bubble model, NOAA's oxygen limits — and our guides cite them by name rather than asking you to trust us. Second, validate against references: the deco engine is checked against established dive software and regression-tested on every change — the details are on how we validate.
What DecoLog is not
DecoLog is a planning aid. It is not a dive computer, not a training course, and not a substitute for either. Every schedule it produces is a model's opinion, and models are approximations of a messy physiological reality — verify plans independently, dive a functioning computer, and stay within your certification.
⚠ Planning aid only — not a substitute for a dive computer or proper training. Questions or corrections? Reach us via the Field Notes Telegram channel.