What is the difference between masking an element and blocking it?

Masking keeps the structure of the element and replaces only the characters, so the replay still shows where the visitor typed and how they moved through the form. Blocking leaves the element out of the recording entirely and the replay shows an empty area, which suits regions whose layout and size should not be captured either.

Does adding a masking rule affect recordings already captured?

No. Masking is applied at recording time inside the visitor's browser, so a new rule only affects sessions recorded afterwards. For recordings captured before the rule existed, deleting those recordings is the only remedy.

Replay Masking

Intermediate

Updated Jul 11, 2026 Shahin editorial 2 min read

PronunciationEN/ˈriːpleɪ ˈmæskɪŋ/

Replay masking is the set of recording-time rules that replaces sensitive on-page content with placeholders before a session recording leaves the browser.

The recorder does not capture pixels. It captures a structural description of the page and rebuilds it in a player, and masking is applied to that description: text nodes carrying a marked class become placeholders, form inputs are hidden by default, and elements marked as blocked are never serialised at all. Because the substitution happens inside the visitor's browser, the original characters are never transmitted or stored, which is what separates masking from redaction applied later on the server. The common failure is assuming the defaults are enough: an order total rendered as ordinary text, a national ID printed on a confirmation page, or a token sitting in a query string are none of them form inputs, and each needs an explicit rule.

FAQ