Rakuten SubID Guide

What a SubID actually is

Think of a SubID like the table number a waiter writes on your order slip. The kitchen doesn't just need to know "an order came from the restaurant" — it needs to know it came from table 12 so the food gets to the right people. A SubID does the same job for affiliate clicks. The publisher tags each link with a short label, that label rides along with the click into Rakuten's system, and when a sale happens the label lands right beside it in the transaction report.

In Rakuten's world this label lives in a link parameter called u1. You'll sometimes hear it called "SID" or just "sub ID," but it's the same idea: a free-text field the publisher controls and fills with whatever they find useful — a page name, a campaign code, an email send date, a product category, and so on. Rakuten doesn't dictate what goes in there; it simply carries the value through and reports it back.

The important thing to understand as an advertiser is that you don't set the SubID — the publisher does. Your job is to read it, understand the conventions your partners use, and make sure your reporting and any postbacks actually capture it.

Why it matters to you

Without SubIDs, your partner reporting stops at the publisher level. You can see that a cashback site or a content blog sent you 40 sales last month, but you can't see what inside that site did the work. That blind spot quietly costs money, because it stops you negotiating, optimising, or paying smarter.

With SubIDs flowing into your reports, you can suddenly answer questions that change budgets: which articles convert, whether a publisher's homepage placement beats their deal pages, whether a particular newsletter slot is worth a higher rate, and whether "incremental" partners are really sending new customers or just intercepting people already heading to checkout. That granularity is what lets you reward the placements that grow the business and trim the ones that don't.

How it works, step by step

1. The publisher builds a tracking link to one of your pages and appends a SubID value in the u1 field — for example u1=winter-coat-review.
2. A shopper clicks the link. Rakuten records the click and stores the SubID value against it, alongside the publisher ID and timestamp.
3. The shopper browses and (hopefully) buys on your site. Your Rakuten tracking tag fires on the confirmation page and reports the order.
4. Rakuten matches the order back to the original click using its cookie or tracking method, and pulls the stored SubID through to the transaction.
5. The SubID appears in your reporting as a column or filter on the relevant performance and transaction reports.
6. You analyse it — grouping sales by SubID to see which placements produced revenue, average order value, and return rates.
7. (Optional) You pass it onward. If you run a postback or send conversion data into your own analytics, you capture the SubID so it lines up with your internal numbers too.

Notice that every step except your analysis depends on the publisher having tagged the link well in the first place. If they leave u1 blank, the field simply comes through empty — there's nothing to recover after the fact.

Common mistakes

• Assuming the SubID is yours to control. It belongs to the publisher. If you need a specific placement broken out, you have to ask the partner to tag it — you can't backfill it from your side.
• Treating an empty SubID as "no data." A blank u1 usually means the publisher didn't tag that link, not that the sale is untracked. It's a prompt to nudge the partner, not a reason to discount the sale.
• Reading raw SubID values as meaningful without context. One publisher's u1=123 and another's u1=123 mean completely different things. Always analyse SubIDs within a single publisher, never pooled across all of them.
• Forgetting that SubIDs can carry personal or messy data. Some publishers stuff user IDs or long strings into the field. Don't build dashboards that expose raw values publicly, and expect to do some cleanup before grouping.

Reporting tips

In the Rakuten advertiser dashboard, the SubID surfaces on transaction-level and performance reports — look for a column or filter labelled u1 or "SubID." Start by filtering to a single high-volume publisher and grouping their sales by SubID; that's where the story is clearest. Pay attention not just to order counts but to average order value and return/cancellation rates by SubID, because a placement that drives lots of low-value, high-return orders can look great on volume and poor on profit.

If you export transactions to a spreadsheet, the SubID becomes a pivot dimension — sort placements by net revenue and you'll quickly see the 20% of placements doing 80% of the work. Save these as recurring reports so you can spot when a strong placement drops off (often a sign the publisher changed or removed a link).

When to use it — and when not to

Related guides

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