How can I read http errors when responseType is blob in Axios with VueJs?
Stefan Bogdanescu
Founder & Senior Architect · 2026-06-29
# Mastering Axios Errors with Blob Responses in Vue.js
As developers working with modern asynchronous requests in frameworks like Vue.js, dealing with HTTP errors can often become a frustrating maze. One specific scenario that trips many up is when using `responseType: 'blob'` with Axios. When an error occurs (e.g., a 401 Unauthorized or 500 Server Error), we expect to read the status code and the error message, but because the successful response was treated as a binary blob, accessing this information within the `.catch()` block proves challenging.
This post dives deep into why you face this issue and provides robust, practical solutions for correctly reading HTTP status codes when dealing with Blob responses in your frontend applications.
## The Challenge: Why `responseType: 'blob'` Complicates Error Handling
When you set `responseType: 'blob'`, Axios receives the response body as a raw binary stream rather than parsed JSON or text. If the server returns an error status code (like 401 or 500), Axios throws an error, but the structure of that error object can be confusing regarding where to find the status code and the error payload.
Your attempt to read `error.data` fails because `error.data` often contains information about the request failure itself, not the original response body you were expecting (which is the Blob). Trying to treat the entire error object as a blob as shown in your example doesn't correctly extract the HTTP status code embedded within Axiosâs error structure.
## The Correct Approach: Inspecting `error.response`
The key to reliably extracting HTTP status codes and error details lies not in trying to parse the initial Blob directly, but in inspecting the specific properties Axios attaches to the error object when a response is receivedâspecifically, `error.response`.
When an HTTP error occurs (status code 400 or higher), Axios populates the `error.response` property with the full response details, including the status code and the data stream (which might be a Blob in this case).
Here is the recommended pattern for handling errors robustly:
```javascript
import axios from 'axios';
async function downloadBlob(url) {
try {
const response = await axios.get(url, {
responseType: 'blob' // Requesting binary data
});
// Success case: Process the Blob directly
const blob = response.data;
console.log('File downloaded successfully.');
// Code to create URL and trigger download here...
return blob;
} catch (error) {
// Error Handling Block
if (error.response) {
// The request was made and the server responded with a status code
const status = error.response.status; // <-- This holds the HTTP status code!
const errorData = await error.response.text(); // Read the response body as text
console.error(`HTTP Error: Status ${status}`);
// Throw a custom, meaningful error based on the status
if (status === 401) {
throw new Error('Unauthorized: Please log in again.');
} else if (status >= 500) {
throw new Error(`Server Error: Something went wrong on the server (Status: ${status}).`);
} else {
// Handle other client errors (400, 404, etc.)
throw new Error(`Client Error: Request failed with status ${status}. Details: ${errorData}`);
}
} else if (error.request) {
// The request was made but no response was received (network error)
throw new Error('No response received from the server.');
} else {
// Something happened in setting up the request that triggered an Error
throw new Error(`Axios Setup Error: ${error.message}`);
}
}
}
// Example usage in a Vue component/method:
downloadBlob('your-api-endpoint').then(blob => {
// Handle successful blob data
});
```
## Best Practices for Laravel and API Integration
When building APIs using frameworks like Laravel, ensuring your backend correctly returns meaningful JSON error messages (even on failure) is crucial. If your Laravel application throws an exception, ensure that the exception handler serializes it cleanly into a standard HTTP response format. This allows frontend tools like Axios to reliably parse `error.response.data` as predictable JSON objects, regardless of whether you are handling file downloads or standard data requests.
For complex API interactions involving status codes and structured responses, always lean on the structure provided by Axios (`error.response`) rather than trying to manually reconstruct data from raw Blob streams within the error handler. This keeps your frontend code clean, predictable, and highly maintainable, aligning with the principles of building robust systems, much like the architecture promoted by technologies found in the Laravel ecosystem.
## Conclusion
Dealing with `responseType: 'blob'` errors requires shifting focus from reading the initial raw error object to inspecting Axios's dedicated response structure (`error.response`). By checking for the existence of `error.response` and extracting `error.response.status`, you gain complete control over handling HTTP failures, allowing you to throw specific, contextual errors based on the server's status code. This approach ensures your Vue.js application provides clear feedback to the user while maintaining a clean separation between successful data handling and error management.