Please read this before relying on anything Fennel shows you.
Fennel is a diary. You log meals, symptoms and stool form, and it reports how often your symptoms followed particular foods and FODMAP groups, inside fixed time windows, with the sample sizes shown. It is a counting and statistics tool built on your own records and on published, openly available food information.
Everything the app reports is an association between two things you logged. A symptom that followed a meal may have been caused by that meal, by something else you ate, by stress, by sleep, by your cycle, or by nothing identifiable at all. Fennel shows the counts on both sides, names the window it used, and flags runs of days that were unusually stressful or fell in a cycle phase, so a reading can be checked rather than believed. It reports nothing at all until there is enough data behind it, and it says how much more it needs.
This is the app's central rule rather than a disclaimer. It never labels a food, never colours one good or bad, and never tells you to avoid anything. Colour marks how strong the evidence is and nothing else. What to do about a pattern is a decision for you, with your clinician or dietitian.
The program schedules challenge days and rest days and records what you logged on them. It is bookkeeping to run alongside professional advice, not a protocol prescribed by this app. Phase lengths appear as ranges because the sources state them as ranges, and the sources are one tap away on the screen. Long term dietary restriction has real nutritional and microbiome costs, and the app says so where the elimination countdown lives. Please do not run a restrictive diet from an app alone.
If you log blood in your stool, a fever alongside gut symptoms, or unintended weight loss, Fennel shows one card suggesting you discuss it with a clinician and cites where that comes from. It will not tell you what it might mean, because it cannot know. If you feel unwell or have any symptom that worries you, contact your clinician or your local emergency service. Do not use this app to decide whether to seek care.
Food tags are drawn from the public sources listed on the Sources page and each one links the source on the screen that makes the claim. FODMAP content varies with variety, ripeness, portion and preparation, and published figures differ between sources. Some rows in the food list are marked as under review while a registered dietitian works through them; those rows carry the same citations as every other row, and any tag can be reported as wrong. All of it is a snapshot taken when the app version was built.
Everything you log stays on your device and you can export all of it as a CSV file at any time, free. See the Privacy Policy. There is no sync in this version, so a lost or wiped phone means a lost diary: export it if it matters to you.
Fennel is provided as is, without warranty of any kind. To the fullest extent permitted by law, the developer is not liable for any loss or damage arising from use of the app or reliance on the information it shows. Nothing in these terms limits liability where it cannot lawfully be limited, including for death or personal injury caused by negligence.
Pro is optional. It is sold either as an auto-renewable subscription, billed weekly, monthly or yearly, or as a one time purchase that never renews. Prices are shown in the app in your own currency before you buy, and any free trial is stated on the purchase screen. A subscription renews automatically at the end of each period unless it is cancelled at least 24 hours before the period ends, and your account is charged for renewal within 24 hours of the end of the current period. You can manage or cancel a subscription in your Apple account settings after purchase. Logging, the day timeline, the calendar, CSV export and the app lock are free and unlimited and are not part of any paid tier.
Your use of the app is also subject to the Apple Media Services Terms and Conditions, which for auto-renewing subscriptions include the standard end user licence agreement at apple.com/legal/internet-services/itunes/dev/stdeula.
Fennel is made by an independent developer. Last updated 30 August 2026.