What is Affiliate Marketing?

Affiliate marketing is a performance-based model in digital marketing. A company, the merchant or advertiser, pays third parties a commission for every sale, lead or click they generate. Those third parties are called affiliates or publishers: a blog, a YouTube channel, a price comparison site or an account with its own audience.

The relationship between the two rarely runs directly. An affiliate network usually sits in between: a platform that centralises available programmes, generates the tracking links and handles commission payouts to each affiliate. Networks such as Awin, Rakuten Advertising or TradeDoubler work this way: the merchant lists its programme, sets the commission, and the network runs the technical infrastructure.

The affiliate needs no stock, no order fulfilment and no payment processing. Their job is to send qualified traffic to the merchant, and in exchange they receive a share of every result their link produces. The model is especially common in categories with heavy pre-purchase research, such as software, travel, finance or electronics, where buyers actively look for comparisons and first-hand reviews before deciding.

PPS dominates because it ties the merchant's cost to a real business outcome. PPC is the riskiest model for the merchant, since it pays for clicks even when they never turn into a sale.

Once an affiliate joins a programme, they receive their own affiliate link: the product URL with an identifier attached, or a deep link that points straight to a specific product page instead of the homepage.

When someone clicks it, the merchant's server stores that identifier in a cookie on the user's browser. That record is what allows a later purchase to be attributed to the right affiliate, even if the sale closes hours or days after the click.

That period is called the attribution window: the length of time during which a purchase is still credited to the affiliate who sent the visit. Most programmes set it between 24 hours and 30 days, though some extend it for products with a longer decision cycle. Once the window closes, the cookie expires and that sale no longer earns a commission, even if the user buys shortly after. Most programmes also apply a last-click attribution model: when a user clicks links from several different affiliates before buying, the full commission usually goes to whoever generated the last recorded click before the sale.

The affiliate network acts as the technical middleman: it runs the tracking system, reconciles sales against the original clicks and pays out each affiliate's agreed commission, in a role similar to how a CRM centralises a company's contact data.

The most important technical point in affiliate marketing is the rel="sponsored" attribute. Google introduced it in 2019 as a more precise counterpart to the generic nofollow, built specifically for paid or compensated links such as affiliate links.

Under Google's guidelines for outbound links, every affiliate link, meaning any link for which the publishing site earns a commission when a click, lead or sale is generated, must carry rel="sponsored" on the <a> tag rather than a plain dofollow attribute. An affiliate link left unmarked breaches Google's link spam policies, and systematic use of unmarked links can trigger a manual action against the site.

rel="sponsored" is a technical obligation toward Google, separate from the legal disclosure obligation toward the reader. Consumer protection law, including within the EU, requires a clear notice whenever content contains affiliate links, usually a visible line such as "this article contains affiliate links". Meeting one obligation does not satisfy the other.

• Mark every single affiliate link with rel="sponsored" on the <a> tag, with no exceptions, even when nofollow is also set.
• Place a visible affiliate disclosure before the reader reaches the first link.
• Test the product yourself before recommending it: a review with your own screenshots and real usage data converts better than copy lifted from the merchant.
• Check the CTR of each link separately to see which recommendations actually drive clicks, not just which page gets the most visits.
• Pair the main link with a cross-selling suggestion where it fits, instead of pushing a single product.
• Match the content to the stage of the customer journey: a comparison piece works better at the decision stage than a generic discovery article.

• Publishing product descriptions and reviews copied word for word from the merchant, with no testing, comparison or first-hand experience: Google classifies this as thin affiliation and can demote the page.
• Forgetting rel="sponsored" on older links when an article is updated with new affiliate products.
• Hiding the commercial relationship from the reader even when the link carries the correct technical attribute: the obligation toward Google and the obligation toward the user are two different things.
• Choosing products purely for their commission rate without checking they fit what the site's audience is actually looking for.
• Not auditing links regularly: a discontinued affiliate programme leaves behind dead links or redirects to irrelevant pages.