How to Fix the Warning: Text Content Did Not Match Error in SSR Apps
If you are developing a server-side rendered (SSR) application with React, Express, and Apollo, you might encounter an error message that states:
Warning: Text content did not match. Server: "SOME DATA" Client: "Loading..."This error typically occurs when there is a mismatch between the server-rendered content and the content rendered on the client side. It is a common issue in SSR apps and can be easily fixed. In this article, we will show you how to resolve this warning and ensure proper content hydration.
The Issue: Data Mismatch between Server and Client
When the SSR app initially loads, the content is rendered on the server-side and sent to the client. However, when the client bundle is loaded, it might attempt to refetch data, leading to the mismatch warning. The error usually manifests as the loading flag being set to different values, such as “Loading…” on the server and “SOME DATA” on the client.
The error arises because the server-rendered HTML, which contains the initial data, is not properly rehydrated on the client-side. To fix this, we need to ensure that the client side of the app rehydrates the server-side values and does not trigger the loading flag on the initial load.
Solution: Skipping Queries for Server-Side Rendering
React Apollo provides a mechanism to explicitly mark components for server-side rendering. By setting the ssr prop to false in the Query component, we can skip queries during server-side rendering and allow the client to load the data independently.
To implement this solution, follow these steps:
Step 1: Update the Client-Side Code
// client.js
const httpLink = createHttpLink({
uri: "http://10.10.10.139:4000/"
});
const client = new ApolloClient({
link: httpLink,
cache: new InMemoryCache().restore(window.__APOLLO_STATE__)
});
ReactDOM.hydrate(
<ApolloProvider client={client}>
<BrowserRouter>
<div>{renderRoutes(RoutesList)}</div>
</BrowserRouter>
</ApolloProvider>,
document.getElementById("root")
);Step 2: Modify the Query Component
// index.js
<Query query={GET_USERS} ssr={false} variables={queryVariables}>
{({
loading,
error,
data
}) => {
if (loading) return <p>Loading...</p>;
if (error) return `Error: ${error}`;
return data.users.map(user => <p key={user.id}>{user.login}</p>);
}}
</Query>By setting ssr={false} in the Query component, the data will not be loaded during server-side rendering, preventing the mismatch between server and client content.
Conclusion
Server-side rendering is a powerful technique for improving the performance and SEO of React applications. However, handling data hydration during the transition from server to client can be tricky and may result in warning messages like “Warning: Text content did not match.” By using the solution provided above and skipping queries during server-side rendering, you can ensure a smooth transition and avoid these errors in your SSR apps.
Remember to update the client-side code and modify the Query component to implement this solution effectively. With proper data hydration, your SSR app will render without any mismatch warnings, delivering a seamless user experience.
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