Values added after a question mark in a URL, often used for filtering, tracking, sorting, or pagination.
URL parameters are values in a URL’s query string, commonly written after a question mark. In /products/?color=blue&sort=price, color and sort are parameter names, and blue and price are their values. A website decides what those values do; the punctuation does not tell a search engine whether a variation is important.
Some parameters change the content, such as a filter that shows a specific product range. Others change its order or record campaign information. A tracking variation may display the same page as the clean URL, while a filter may produce genuinely different results. Treating every parameter alike can break useful features or create large numbers of redundant addresses.
The SEO question is which variations should be discoverable and treated as separate search destinations. Decisions about internal links, canonical URLs and crawling need to follow the actual content and business purpose. Parameters are not automatically bad, and deleting them blindly can remove the visitor’s intended selection.
Takeaway: Know which parameters change a customer’s view and which only record tracking. That distinction helps you manage duplicate URLs without damaging product filters or campaign measurement.
Example
A shop emails a link containing a campaign-tracking parameter. The product description remains unchanged. Its blue-only category filter, however, changes the products displayed. These two URLs need different analysis even though both contain a question mark.
What to check
Inventory a few real parameter combinations and open them as a customer would. Record whether content, sorting or tracking changes before asking your developer to consolidate URLs or restrict crawling.
For more detail, see Google URL structure guidance.