Multiplayer vs Fullstory

Session replay tools have become a key component of testing and debugging workflows in recent years. These tools recreate user interactions on web and mobile applications to give developers, product owners, and test engineers insights into user behaviour and provide debugging context. Multiplayer and Fullstory are two such popular tools. In this article, we’ll go through each tool and compare their capabilities to help you decide which one to pick.

Multiplayer

Multiplayer is a full-stack session recording tool that provides engineers with complete, correlated replays, capturing everything from the frontend to the backend, without requiring external integrations. Multiplayer natively supports all observability stacks, giving you full debugging context from day one. The tool aims to create a platform for collaboration between QA, developers and users in order to accelerate debugging and feature production. Multiplayer supports users in the following manner:

QA engineers: Automatic step-by-step capture of issues, the moment they occur, limiting the need for elongated reproduction and investigation.
Developers: Complete error tracing that is both full-stack and AI-ready, for contextual debugging.
End-users: Easy bug reporting and less time spent on explaining issues to support engineers.

Fullstory

Fullstory is a behavioral analytics and UX optimization platform that also provides session replays; however, recordings are limited to frontend data. Capturing frontend data helps QA recreate issues, developers solve frontend bugs, and marketing and UX teams investigate user behaviour. While these features are valuable, debugging with only frontend context provides developers with only a part of the puzzle, especially while trying to solve issues that span across the tech stack.
Feature Comparison

Let’s analyze Multiplayer and Fullstory’s features by using a simple example: an online e-commerce platform is trying to understand why their “add to cart” button is not adding any items to users’ carts.

Session Capture

Multiplayer allows users to capture sessions through their browser extension, in-app widget, or automatic capture by integrating a library SDK. Multiplayer can be either self-hosted or cloud-hosted.

The individual who identified the ‘add to cart’ issue could simply click on the record button and provide developers with the full context of the bug. If error-triggered recording is activated (continuous recording), the session would automatically be recorded and flagged. Teams can also decide to enable c*onditional recording* if users frequently interact with critical data and would like all sessions to be recorded.

Fullstory can be installed only via SDK and deployed as a SaaS solution. Fullstory thus captures all incoming data. The recorder would have to manually search the list of all session recordings and filter by console error or timestamp to find it again.

Collaboration across teams

After the session has been captured, support engineers would likely escalate the bug to developers, once they have confirmed that the ‘Add to cart” button is behaving incorrectly.

Multiplayer provides a link to each session recording, which contains user actions, UI state, visible errors, and system-level telemetry. This link can be included in the respective ticketing system that the firm uses (e.g., Zendesk, Jira). In addition, the support engineer can also choose to annotate over the session recording to highlight unexpected behaviour and UI issues, or add comments to specific data points (APIs, spans, traces).

Fullstory would first require a support agent to skim through its playlist of sessions or filter all sessions using an associated timestamp, user ID, or search for ‘rage clicks’, after being informed of a bug by a user.

Once they have found the session in question, they can extract a shareable link from it and include it in the development ticket. This link contains only frontend UI events and a field to enter a note in.

Debugging

Let’s assume the ‘add to cart’ button was not doing anything due to a backend cache invalidation issue, where the actual stock of the item was 0, but showing as available to users, and allowing them to click “add to cart” (without anything actually happening).

// Backend Bug: Cache not invalidated when stock changes
@Cacheable(value = "products", key = "#productId")
public Product getProduct(String productId) {
    return productRepository.findById(productId).orElse(null);
}

// When inventory updates, cache is not cleared
public void updateStock(String productId, int newStock) {
    Product product = productRepository.findById(productId).orElse(null);
    product.setStockQuantity(newStock);
    productRepository.save(product);
    // Missing: @CacheEvict to clear stale cache
}

In the above Java snippet, we see that when a stock is updated, a cache eviction strategy is missing, causing the frontend code to still believe that the product is available.

Multiplayer allows a developer to immediately find the relevant session recording, as it has been automatically captured when the error occurred. Using OpenTelemetry, when a frontend action triggers a backend call, the trace context (trace ID, span ID) is automatically propagated via HTTP headers, which can then be viewed on a unified frame by the developer. The developer would look at the stack trace and see no error with the frontend user action and associated headers, but quickly notice that the associated backend API call produces an “insufficient stock” error response message. His or her first instinct would be to investigate the inventory API calls.

Furthermore, if the developer is using an AI code assistant, they can leverage the Multiplayer MCP server to feed it with complete system context and make debugging even quicker.

Fullstory would first require a developer to skim through its playlist of sessions or filter all sessions using an associated timestamp, user ID, or search for ‘rage clicks’. He or she would then see that frontend-wise, there are no apparent issues. The developer would have to then copy the timestamp of the error and session metadata, open the backend tracing service (if any), and grep through backend logs to find the associated backend API call. While this method would still be successful, it would be time-consuming and involve frequent tool-hopping.

The root cause analysis with Multiplayer took about 3 minutes, and Fullstory took about 15. We can then add cache invalidation by simply adding the following line above the updateStock function.

// Backend: Add cache eviction when updating stock
@CacheEvict(value = "products", key = "#productId")
public void updateStock(String productId, int newStock) {
    Product product = productRepository.findById(productId).orElse(null);
    product.setStockQuantity(newStock);
    productRepository.save(product);
}

Note: When using Multiplayer, the developer can auto-generate a runnable test script from this session to ensure that the “Add to cart” button does not fail due to a stale cache.

Conclusion

When to use Multiplayer:

• When you want to improve the debugging process for developers by quickly providing full stack context and reducing the time taken to conduct an RCA (Root Cause Analysis).
• When your application has a complex backend system, and bugs typically span across various services.
• When cross-team communication (support-development) is vital to solving user issues.
• When your teams use AI coding assistants such as Cursor, Claude Code, etc.

When to use Fullstory:

• When session recordings are primarily for UX analytics and to understand UI behaviour.
• When your application is frontend-heavy, and backend tracing is not a priority.
• When product managers and marketing teams are your primary user base for session recordings.