Overview

Session Replay expands your user experience monitoring by allowing you to capture and visually replay your users' web browsing or mobile app experiences. Session Replay is available in both RUM and Product Analytics, helping you identify and reproduce errors, understand user journeys, and gain insights into your application's usage patterns and design pitfalls.

Mobile Session Replay

Mobile Session Replay expands visibility into your mobile applications by visually replaying each user interaction, such as taps, swipes, and scrolls. It is available for native apps on Android and iOS, Kotlin Multiplatform, React Native, and Flutter. Visually replaying user interactions on your applications makes it easier to reproduce crashes and errors, as well as understand the user journey for making UI improvements.

How the Session Replay recorder works

The Session Replay recorder is built into the RUM Mobile SDK. Unlike web browsers, mobile apps don't use HTML or CSS. Instead, the recorder takes a "snapshot" of your app's screen by breaking it into rectangles called "wireframes." It then keeps track of changes by only updating the wireframes that have changed, making the process efficient and fast.

Wireframe concept

A wireframe is like a digital sticky note marking a specific area of your app's screen, such as a button, image, or background. Each wireframe is a rectangle that helps the recorder keep track of what's on the screen.

Examples of wireframes:

• A text label becomes a "text" wireframe, defined by its position and size.
• The app's background is a "shape" wireframe—a rectangle that covers the whole screen.
• Any container with a solid background is also a "shape" wireframe.
• Images or icons are "image" wireframes, which can include style details like transparency.
• Even complex elements, like a map with many parts, can be combined into a single "image" wireframe.

Recording algorithm

The recorder scans your app's screen from the background to the front, looking for all the visible parts. It creates a wireframe for each one. For example, a screen with 78 different elements can be simplified into 25 wireframes:

Wireframes are recorded in the order they appear on the screen (from back to front) and are placed using exact screen positions. There's no complicated tree structure, only a flat list of rectangles.

Rendering algorithm

When you watch a replay, Datadog's player rebuilds the screen by drawing each wireframe in order. It uses the position and size of each rectangle to put everything in the right place. The first wireframe sets the screen size and orientation (portrait or landscape).

Each new wireframe is drawn on top of the previous ones, like stacking transparent sheets. This lets the player show things like overlapping or semi-transparent elements correctly.

For instance, the screenshot displayed above is reconstructed in 25 passes:

Iteration	1	2	3
Viewport

The first wireframe dictates the viewport size, enabling the Session Replay player to properly represent the device's screen size and orientation (landscape / portrait).

Iteration	4	5-11	12-13
Viewport

Because wireframes are sorted in back-to-front order, the player redraws the existing portions of the frame, which is desirable because it supports several UI patterns (such as semi-transparent elements).

Iteration	14-25	Final result
Viewport

Full and incremental snapshots

A "full snapshot" is like taking a picture of the entire screen, with all its wireframes. But to save time and data, the recorder usually sends "incremental snapshots", which are updates that include only the wireframes that have changed.

Each wireframe has a unique ID (like a name tag), so the recorder knows exactly which ones to update. For example:

• If a wireframe moves, only its new position and ID are sent.
• If a wireframe disappears, the update says which ID was removed.
• If only the content changes (like new text), the update includes the new content and the wireframe's ID.

Below are examples showing how incremental snapshots only send updates for impacted wireframes.

Example	Description
	If a wireframe position changes, but its content and appearance aren't altered, the incremental snapshot only needs to include new positions for impacted wireframes and their UUIDs. This might correspond to a "slow scrolling" scenario or any other scenario where only a portion of the screen is moved.
	If a wireframe disappears from the screen, an incremental snapshot may only include information on removed UUIDs. Alternatively, the snapshot could always include information about the remaining UUIDs.
	If only the content of a wireframe changes, an incremental update includes only the new content and the UUID of the altered wireframe.

In summary, the Session Replay recorder breaks your app's screen into rectangles called wireframes. It only tracks and sends updates for the parts that change, making replays efficient and accurate.

Mobile Session Replay is not available for smart TVs or wearables.

AI-powered summaries and smart chapters

Summaries and smart chapters give you context about what happened in a session before you watch it.

Summaries describe the user's intent, key actions, friction signals, and outcome. Specific moments in the summary are hyperlinked so you can jump directly to that point in the replay. In the session list, hover over a replay to preview the summary, or open the replay directly. If a session has been summarized before, the summary appears instantly when you open the replay.

Smart chapters automatically segment the replay timeline into labeled stages of the user journey. For example, in an ecommerce session, chapters might include "Browse lighting", "Shop bedding and chairs", and "Review cart and checkout". Chapters appear when you hover over the timeline and in the dropdown on the player controls, letting you jump directly between them.

AI summaries and smart chapters are generated for sessions with at least four user actions and a duration of at least 45 seconds.

Comments

Session Replay comments allow your team to collaborate on bugs, usability issues, and other observations directly within a replay.

With comments, you can:

• Add a comment at a specific timestamp on the replay timeline. Comment markers appear on the timeline and the Comments tab.
• @mention a teammate or team in a comment. Tagged users receive an email notification with a link that opens the replay at the commented timestamp.
• Copy a link to any comment and share it externally. The link opens the replay at the annotated moment with that comment thread open.
• Reply in-thread to collaborate within a replay, and edit or delete your own comments as needed.

To find replays that need your attention, use the All mentions to me and Commented replays default playlists. See Session Replay Playlists for details.

Extend data retention

By default, Session Replay data is retained for 30 days.

To extend Session Replay data retention to 15 months, you can enable Extended Retention on individual session replays. These sessions must be non-active (the user has completed their experience). You need the rum_extend_retention permission to enable Extended Retention.

To access any Session Replay at a later time, Datadog recommends saving the URL or adding it to a Playlist.

Extended Retention only applies to Session Replay and does not include associated events. The 15 months start when Extended Retention is enabled, not when the session is collected.

You can disable Extended Retention at any time. If the session replay is still within its default 30 days of retention, the replay expires at the end of the initial 30 day window. If you disable Extended Retention on a session replay that is older than 30 days, the replay immediately expires.

See the diagram below to understand what data is retained with extended retention.

Playback history

You can see who has watched a given session replay by clicking the watched count displayed on the player page. This feature allows you to check whether someone you'd like to share the recording with has already watched it.

The history includes only playbacks that occurred in the player page or in an embedded player, like in a Notebook or side panel. Included playbacks also generate an Audit Trail event. Thumbnail previews are not included in history.

To view your own playback history, check out the My Watch History playlist.

Playlists

You can create a playlist of Session Replays to organize them by any patterns you notice. Learn more about Session Replay Playlists.

Dev Tools

Dev Tools is a built-in debugging panel in Session Replay that exposes key information during playback. Use it to identify issues, trace requests, and understand performance bottlenecks, all without reproducing the issue yourself. Dev Tools are available for RUM sessions.

Learn more about Dev Tools.

Further reading