How Truesize works

Truesize adds a size advisor to your product pages. A shopper answers a few quick questions and gets the size most likely to fit, instead of guessing. Fewer wrong sizes means fewer returns, less work for your team and happier customers.

This guide explains what happens behind the scenes, so you know what to expect and how to get the best results. It is written for shop owners and teams, not developers. For step-by-step help with the dashboard, read the Company dashboard guide.

The big picture

Four parts work together:

Part	What it is	Who looks after it
The widget	The "Find my size" button and the questions shoppers see on your product page.	You style it; we run it.
Your catalogue	The products you add, and the sizes each one comes in.	You (by hand, by file, or from your shop).
Your orders	Which size shoppers bought, and whether they kept it or sent it back.	Your shop reports this to us.
The engine	The part that compares a shopper with people like them and picks a size.	Truesize.

You do not need to build anything to start. Add a few products, paste one line of code on a product page, and the advisor works from day one. It then gets more accurate as your orders come in.

What a shopper sees

1. The shopper presses Find my size on a product page.
2. A short, friendly window asks about their height, weight and age, and how their body is shaped around the tummy and chest.
3. Optional questions come next, such as the brand and size they usually wear or a size they bought from you before. Each one makes the answer more accurate, and each one can be skipped.
4. They see one recommended size, how confident we are, and the choice to select it. If two sizes are a genuine toss-up, we say so.

It takes under a minute, works on phones, and can speak many languages, including right-to-left languages such as Arabic. You choose the language in the dashboard, and the page can also pass a language to the widget.

How we choose a size

For every shopper we use the best method available, in this order.

1. Shoppers like you (the best answer)

We look through the orders that were kept (not returned) for people with a similar height, weight, age and body shape, and see which size they kept. The closest matches vote, and the size with the most votes wins. We need a reasonable number of similar shoppers before we trust this, so it becomes available as your orders build up. The answer is based on real people who bought and kept the item, not on a size chart.

2. A size the shopper already knows

If the shopper tells us a size they bought from you before and it fitted, we start from that. This is a strong signal, so we use it with good confidence.

3. Your size chart (the starting point)

When there are not enough orders yet, we use a size chart: a table of height and weight ranges for each size. If you have added your own chart in the dashboard we use it, otherwise we use a general one. This is why the first answers show a lower confidence. It is an honest estimate, and it improves as soon as real orders arrive.

Confidence

Every answer shows how sure we are:

• High: many similar shoppers agree.
• Medium: a good match, with some disagreement.
• Low: we are working from the size chart or have few matches.

When two neighbouring sizes are almost equally likely, we say the shopper is between two sizes and show both. You can hide the confidence meter in the widget settings.

How it learns from your orders

This is what makes Truesize better than a fixed size chart. It learns how your products really fit.

1. A shopper uses the advisor and orders a size.
2. Your shop tells us about the order (a developer sets this up once, see the developers guide if you have access, or ask us).
3. We wait for your return window to finish. This is the number of days you give customers to send things back (30 by default, which you can change in Settings), plus a few extra days for delivery.
4. If the item was not returned, it counts as a kept order. Kept orders are the evidence the engine learns from.
5. If it was returned, you tell us why: too small, too big, or another reason.

Products that run small or large

Each night we look at the return reasons for each product. If most size-related returns for a product say "too small", we mark that product as running small and nudge future recommendations up a size (and the same for "too big"). We only do this once there is enough evidence, so a couple of unusual returns will not change anything. You can see these products under Analytics.

Your data and privacy

We designed Truesize so it needs as little personal data as possible.

• No names, no emails. We never ask a shopper for their name, email or address.
• Body measurements are personal data. They are only saved if the shopper agrees with the tick box in the widget. If they do not agree, we still give the recommendation, but nothing about them is stored.
• Stored anonymously. Saved answers are used to improve advice for other shoppers.
• Deleted after 24 months. Saved shopper profiles are removed automatically.
• Your catalogue and orders are yours. Other companies never see them, and your data is never mixed into their recommendations except as anonymous, combined learning where the shopper agreed.
• Your keys protect your account. See below.

You are responsible for telling your shoppers about the advisor in your own privacy policy. Our Privacy Policy explains what we do on our side.

Keys and domains: how your account stays safe

• Your site key goes in the widget code on your pages. It is meant to be visible, so by itself it is not enough: the widget only works on the domains you have registered, so nobody can copy it to another website.
• Your secret key is for your own server only. It lets your shop send products and orders to us. Never put it in a web page, an app, or a public repository. If it leaks, rotate it in the dashboard straight away.
• You can create several keys, set an expiry date, and revoke or rotate a key at any time.

Plans and what counts as usage

Each plan has a monthly allowance of recommendations, a limit on how many domains and products you can add, and a few extras on higher plans (such as detailed analytics and removing the "Powered by" badge). See the pricing section for the current plans.

• A recommendation is counted each time a shopper gets a size. Opening the widget, selecting a size, reporting orders and syncing products are not counted.
• You get an email when you have used 80% and 100% of your allowance.
• Paid plans can go a little over (about 10%) before the advisor pauses, so a busy day does not stop your shop.
• On the free plan the advisor pauses when the allowance is used up, and shoppers see a polite message. It comes back at the start of the next month, or straight away if you upgrade.

Getting started in five steps

1. Sign up for free at auth.truesize.co.uk/register. You get a site key and a secret key straight away, and some sample products to try.
2. Add your products and their sizes: one by one, by uploading an Excel or CSV file, or by syncing from your shop.
3. Add your size chart (optional but recommended) so the first answers are as good as they can be.
4. Register your domain and style the widget to match your shop.
5. Paste the snippet on your product page. Make sure the product ID in the snippet matches the product's ID in the dashboard.

After that, report your orders and returns (ask your developer, or the developer guide if you have access) so the advisor can learn from real purchases.

The Company dashboard guide walks through each of these screens.

Frequently asked questions

Does it work for every kind of product?

It works best for clothing and footwear in common sizes. Tops, bottoms, shoes and basics such as underwear and socks are supported. Products with very unusual sizing may need your own size chart.

Why is my confidence low?

Low confidence is normal at the start. It means the answer comes from the size chart or from few similar shoppers. Add your own size chart, and make sure orders and returns are being reported. Confidence improves as kept orders build up.

Will it slow down my website?

The widget is loaded with a single small script and only does its work when a shopper presses the button. It does not change how the rest of your page loads.

What if a shopper ignores the advice?

That is fine. We record whether the shopper followed the recommendation, so Analytics can show you how return rates differ between shoppers who followed it and those who did not.

Can I try it without a shop?

Yes. Try the live demo to see the advisor on a pretend store, or sign up and use the sample products.

Who can see my numbers?

Only people with a login to your company account, and Truesize staff who support the service. Other companies never can.

I need help

Use the Contact page. Include your company name and the page or product you are asking about.