Methodology
What this page covers
Our how we rank page explains the method in plain English. This page is the technical version: exactly where the data comes from, the formulas we run, and how you can verify any number yourself.
How the data flows
Catalogue syncWe pull plans and prices from provider catalogues through automated feeds, never by typing numbers in.
NormalisationEvery plan is reduced to the same fields: data amount, validity, price, coverage, 5G, top up and hotspot support.
Price mathsWe compute price per GB = plan price divided by usable data in GB, where usable data is the smaller of the plan's data and 3 GB for every day of validity, rounded to the cent, at the moment of the check. The seller's plain sticker rate is stored alongside it for reference. The rule is enforced inside the database itself, so no import path can bypass it.
SnapshotEach check writes a timestamped record of every country's cheapest rate. That timestamp appears on every page.
How price movement is measured
Movement compares the latest snapshot against the previous one, per country. A green arrow with a percentage means the cheapest rate genuinely fell between two timestamped checks. A red arrow means it rose. A dot means it did not move. We never display a movement that the snapshot history cannot back, which is why arrows only appear when prices actually change.
How provider ratings are computed
Provider star ratings are calculated, not chosen. Which weights apply depends on whether we have enough independent review data to judge a provider's service fairly.
When a provider has at least 25 Trustpilot reviews, the rating uses four components: 40 percent value for money (the provider's median price per GB against the market median), 30 percent country coverage, 15 percent features (5G, top ups, hotspot support) and 15 percent service and reputation, taken from that public review score.
Below 25 reviews the sample is too small to be meaningful, so the service component is dropped rather than guessed, and the remaining three are reweighted to 45 percent value, 35 percent coverage, 20 percent features. A provider is never penalised for having few reviews, and a small review count is never inflated into a service score.
Every provider page states which of the two applies and shows its own component scores as bars, so the number can be checked against the weights. The rating updates automatically whenever prices change, and no human can adjust it.
How we check that a plan is real
Every provider gives us a data feed, and a feed is not a shop. A feed can list a product the seller does not actually offer, describe it differently from the way it is sold, or carry a price that has since moved. A price nobody re-checked is only a number we copied, so we re-check it.
Once a day, after the catalogues are refreshed and before anything is published, each plan is compared against the seller's own destination page: the page a buyer would land on. One of five things happens.
- VerifiedThe seller offers that product at the price we publish. The plan stays, with the date of the check.
- Price movedThey sell it at a different price. We take their price, not ours, and the table re-ranks itself.
- Description correctedTheir feed and their shop describe one product two different ways. We take the shop's description, because that is what a buyer is sold.
- Not foundWe cannot find it on sale. The plan is removed from the site the same day and recorded in our audit log.
- Not yet checkedWe have not built a checker for that seller. The plan stays listed and every page says plainly that it has not been checked.
Two rules keep this honest in the other direction. A checker declares which kinds of product it can actually see on a page, and a plan is only ever marked missing if it is a kind the checker can see, so "we could not check" is never recorded as "it is not there". And if a single check would remove almost everything we hold for a country, we assume we misread the page rather than that the seller emptied its shelves, skip that country and leave it for a person to look at.
Where a seller gives us two sources, we publish only what both of them agree exists. eSIM4Travel is the clearest example: their affiliate catalogue and their own shop disagree, and on the day we added them the catalogue still listed four destinations whose pages had closed and 45 packages at prices that had moved. So a plan appears here only if it is in their catalogue and on their shop, priced at the shop's figure, because that is the number the buyer is charged.
Every provider page publishes what share of that provider's plans have been checked, how many prices we corrected, and how many plans we removed. Where the share is low, the page says so rather than implying more certainty than we have.
What we will not do, whoever asks
These are the rules the site runs on. They apply to advertisers, to affiliate partners, to readers, and to the people who own and build this site.
- Ratings are computed, never editedNo star rating on this site was typed in by a person. Every one is calculated from the published weights, and there is no field in our system to override one. A rating cannot be raised by paying, by partnership, or by asking.
- Rankings follow the mathsTables are ordered by usable price per GB, every provider's best two plans first and the rest after, so one catalogue cannot fill a page. Commission never moves a row, and a provider that pays us nothing outranks one that does whenever the numbers say so.
- Too good to be true is held backAn unverified plan priced under half of every other provider's best rate on a page is listed after the ranked plans as Unverified price, and cannot take the Watchdog Pick or any cheapest figure, until our checker or a person on the team has confirmed it on the seller's own site. The same rule applies to our own partners.
- Findings are published as foundIf a check shows a price is wrong, we correct it to the seller's figure. If a plan is not on sale, it comes off the site. If a provider's terms are unusually strict, the review says so.
- The method changes, not the resultIf a rating looks wrong, the way to change it is to argue the method in public and change it for every provider at once. Adjusting a single score to suit anybody is the one thing that would make every other number on this site worthless.
This is the whole product. A comparison site that edits its own findings is an advertising page with tables on it.
How unlimited plans are handled
A plan without a fixed data amount has no honest price per GB, so we do not invent one. Unlimited plans sort after fixed plans in every table, and the country guides explain the fair use rules that usually apply to them, such as daily full speed caps.
Where the country research comes from
The network, coverage, and local rules content on country pages comes from researched sources: regulators, operators, measurement firms and official guidance, checked at the time of research. Where a fact could not be verified, the field was left empty rather than guessed. Statistics that are old are dated in the text.
How reviews are moderated
Every user review is held unpublished until a human reads it. We reject fake, abusive, or self serving reviews, including providers reviewing themselves or rivals. Providers cannot pay to add, edit, or remove a review.
Check our work
Every page carries the exact GMT timestamp of the last price check. The Price Index can be downloaded as CSV and reused with credit. If you find a number that does not match a provider's checkout, tell us at hello@esimwatchdog.com and we will correct it.