Reading time: < 1 minute
When using axios and attaching a header, like in the following example:
![](https://i0.wp.com/devcodelight.com/wp-content/uploads/2022/09/imagen-12.png?resize=319%2C284&ssl=1)
const config = { headers: { "Content-Type": "application/x-www-form-urlencoded", "TOKEN-AUTH": token } };
We need to be careful with headers that have uppercase letters because axios automatically converts them to lowercase.
If our backend server expects to receive the header TOKEN-AUTH in uppercase, we also need to allow receiving the header token-auth since axios automatically converts headers to lowercase when the app is running on Android/iOS.
The best practice is to avoid using headers with uppercase names to prevent these kinds of errors.
![](https://i0.wp.com/devcodelight.com/wp-content/uploads/2023/07/cropped-light_logo-5.png?resize=100%2C100&ssl=1)