Error handling with error.tsx in NextJS - Step-by-Step Execution

Concept Flow - Error handling with error.tsx

App runs normally

↓

Error occurs in component

↓

Next.js detects error

↓

Render error.tsx component

↓

Show user friendly error UI

↓

User can retry or navigate away

When an error happens in the app, Next.js shows error.tsx to display a friendly message instead of crashing.

Execution Sample

NextJS

'use client';

export default function Error() {
  return <h1>Oops! Something went wrong.</h1>;
}

This code shows a simple error page with a message when an error occurs.

Execution Table

Step	Event	Action	Component Rendered	User Sees
1	App loads normally	Render main page	Main page component	Main page content
2	Error thrown in component	Next.js catches error	Error boundary triggers	No change yet
3	Next.js renders error.tsx	Show error UI	Error component	<h1>Oops! Something went wrong.</h1>
4	User sees error page	User can retry or navigate	Error component	Error message displayed

💡 Error handled by rendering error.tsx, preventing app crash

Variable Tracker

Variable	Start	After Error	Final
errorState	null	Error object	Error object
componentRendered	Main page	Switch to error.tsx	error.tsx

Key Moments - 2 Insights

Why does the app show error.tsx instead of crashing?

Next.js catches errors in components and renders error.tsx as a fallback UI, as shown in execution_table step 3.

Can error.tsx access the error details?

Yes, error.tsx can receive error info via props or hooks, but the simple example just shows a static message (execution_table step 3).

Visual Quiz - 3 Questions

Look at the execution table, what component is rendered right after an error occurs?

A Error component

B Loading spinner

C Main page component

D 404 Not Found page

💡 Hint

Check execution_table row 3 under 'Component Rendered'

At which step does the user first see the error message?

A Step 4

B Step 3

C Step 2

D Step 1

💡 Hint

Check execution_table row 3 under 'User Sees'

If no error occurs, which component remains rendered?

A Error component

B Loading spinner

C Main page component

D Error boundary

💡 Hint

See execution_table row 1 under 'Component Rendered'

Concept Snapshot

Error handling with error.tsx in Next.js:
- When a component throws an error, Next.js catches it.
- Next.js renders error.tsx as a fallback UI.
- error.tsx shows a friendly error message.
- Prevents app crash and improves user experience.
- Customize error.tsx to show details or retry options.

Full Transcript

In Next.js, when an error happens inside a component, the framework catches it and shows a special error page called error.tsx. This prevents the whole app from crashing and gives users a friendly message instead. The flow starts with the app running normally. If an error occurs, Next.js detects it and switches to render error.tsx. The user then sees the error message and can choose to retry or navigate away. The error.tsx component can be simple, like showing a heading with a message. This approach helps keep the app stable and user-friendly even when unexpected problems happen.

Practice

1. What is the main purpose of the error.tsx file in a Next.js route?

easy

A. To catch and display errors that happen in that route

B. To define the page layout and styles

C. To fetch data from an API

D. To handle user authentication

Solution

1. Step 1: Understand the role of error.tsx

   This file is designed to catch errors that occur in its route and show a friendly message to users.

2. Step 2: Compare with other options

   Options A, C, and D describe unrelated tasks like layout, data fetching, or authentication, which are not the purpose of error.tsx.

3. Final Answer:

   To catch and display errors that happen in that route -> Option A

4. Quick Check:

   Error handling = To catch and display errors that happen in that route [OK]

Hint: Remember: error.tsx shows errors in its route [OK]

Common Mistakes:

• Confusing error.tsx with layout.tsx
• Thinking error.tsx fetches data
• Assuming error.tsx manages authentication

2. Which of the following is the correct way to export an error component in error.tsx for Next.js?

easy

A. const Error = () => { Error occurred }; export default Error;

B. function Error() { return Error occurred; }

C. export default function Error() { return Error occurred; }

D. export function Error() { return Error occurred; }

Solution

1. Step 1: Check correct export syntax

   Next.js expects a default export for the error component in error.tsx. export default function Error() { return

   Error occurred

   ; } uses export default function, which is correct.

2. Step 2: Identify syntax errors in other options

   function Error() { return

   Error occurred

   ; } lacks export, so it won't be recognized. export function Error() { return

   Error occurred

   ; } exports a named function, not default. const Error = () => {

   Error occurred

   }; export default Error; misses a return statement inside the arrow function, causing no output.

3. Final Answer:

   export default function Error() { return <p>Error occurred</p>; } -> Option C

4. Quick Check:

   Default export function = export default function Error() { return

   Error occurred

   ; } [OK]

Hint: Use default export function for error component [OK]

Common Mistakes:

• Forgetting to export default
• Using named exports instead of default
• Missing return statement in arrow function

3. Given this error.tsx component, what will be rendered when an error occurs?

export default function Error() {
  return (
    <section role="alert">
      <h1>Oops! Something went wrong.</h1>
      <button onClick={() => window.location.reload()}>Try again</button>
    </section>
  );
}

medium

A. An error message but no button

B. A blank page with no content

C. A console error but no UI change

D. A section with a heading and a button that reloads the page

Solution

1. Step 1: Analyze the JSX structure

   The component returns a <section> with role="alert", containing a heading and a button with an onClick that reloads the page.

2. Step 2: Understand the rendered output

   When an error happens, this UI shows a message and a clickable button that refreshes the page, matching A section with a heading and a button that reloads the page.

3. Final Answer:

   A section with a heading and a button that reloads the page -> Option D

4. Quick Check:

   JSX returns alert section with reload button = A section with a heading and a button that reloads the page [OK]

Hint: Look for JSX elements and event handlers to predict output [OK]

Common Mistakes:

• Ignoring the button's onClick behavior
• Assuming no UI renders on error
• Confusing role attribute with content

4. You wrote this error.tsx but it does not show the error UI when an error happens:

function Error() {
  return <p>Error!</p>;
}
export default Error;

What is the likely problem?

medium

A. The component name must be lowercase

B. The file must be named error.tsx and placed in the route folder

C. The component is not exported as default

D. The component must return a div, not a p

Solution

1. Step 1: Check export and component name

   The component is exported as default and named with uppercase, which is correct.

2. Step 2: Verify file placement and naming

   Next.js requires the error.tsx file to be in the route folder to catch errors there. If misplaced or misnamed, it won't work.

3. Final Answer:

   The file must be named <code>error.tsx</code> and placed in the route folder -> Option B

4. Quick Check:

   Correct file name and location = The file must be named error.tsx and placed in the route folder [OK]

Hint: Check file name and folder location for error.tsx [OK]

Common Mistakes:

• Using lowercase component name
• Returning wrong HTML tags
• Not placing error.tsx in the route folder

5. You want to improve accessibility in your error.tsx component. Which change best helps screen reader users?

hard

A. Add role="alert" to the container element

B. Use only <div> elements without roles

C. Remove all buttons to avoid confusion

D. Use inline styles to highlight the error text

Solution

1. Step 1: Understand accessibility roles

   Adding role="alert" tells screen readers to announce the error immediately, improving accessibility.

2. Step 2: Evaluate other options

   Use only <div> elements without roles lacks roles, reducing accessibility. Remove all buttons to avoid confusion removes helpful retry buttons. Use inline styles to highlight the error text styles visually but doesn't help screen readers.

3. Final Answer:

   Add <code>role="alert"</code> to the container element -> Option A

4. Quick Check:

   Use ARIA roles for accessibility = Add role="alert" to the container element [OK]

Hint: Use ARIA roles like role="alert" for error messages [OK]

Common Mistakes:

• Ignoring ARIA roles for screen readers
• Removing interactive elements unnecessarily
• Relying only on visual styles for errors