A Fair Use Policy (FUP) is the small print on most "unlimited" or "all you can eat" mobile plans. It caps your usage — particularly while roaming — to prevent customers using their home plan as a long-term substitute for a local SIM.
Typical EU FUP
Most UK carriers cap data roaming in the EU at somewhere between 5GB and 25GB per month, even on otherwise-unlimited plans. Once you hit the cap you either get throttled to slow speeds or charged per MB.
Why it exists
Networks pay each other for roaming traffic. If a customer roamed permanently on a £20/month plan, the home network would lose money. FUPs are the limit that keeps the maths working.
How to check yours
Carrier websites publish their FUPs — usually buried in roaming pages. Fuse publishes its FUP openly on every roaming-included plan page.
See also
How Fair Use Policy matters when picking a UK mobile plan
Understanding Fair Use Policy helps you compare mobile providers on a like-for-like basis. Most consumer mobile pricing pages skip the technical detail — knowing the terminology means you can spot when a plan is genuinely better and when it just sounds that way. The Fuse Mobile glossary keeps definitions short and consumer-focused, no jargon-on-jargon.
Fuse Mobile is a UK multi-network data-only eSIM — it gives your phone access to all four UK mobile networks (EE, Three, Vodafone, O2) through a single profile. Where Fair Use Policy is relevant to that setup, it's surfaced explicitly: pricing pages show real numbers, the coverage checker shows live per-network signal, and there's no hidden fee structure. See the plans page for the current pricing or read the multi-network eSIM explainer for the technical detail.