Microsoft 365 Error Codes

Fix HTTP Error 400 Request Too Long When Inserting Pictures in Microsoft 365

Partner Editor Oct 10, 2026 870 views

Question details

Users are encountering an HTTP 400 error when attempting to insert external pictures into Microsoft 365 applications, which cannot be fixed by a basic cache clear or application reinstall.

How to Fix HTTP 400 Request Too Long When Inserting Pictures in Microsoft 365

Product: Microsoft Publisher and Microsoft 365
Device & OS: not provided
Scenario: Inserting an external or online picture into a document using Microsoft 365 applications.
Observed behavior: The application displays a "Bad Request - Request Too Long HTTP Error 400" message and fails to insert the selected picture.

Before you start

Identify the default web browser on your system and the specific external service you are using to search for or insert the picture, as you will need to target its specific site data.

Solution 1Recommended

Delete Specific Site Cookies in Your Web Browser

Removing the oversized or corrupted cookies associated with the external picture service will clear the HTTP 400 request-header error.

The HTTP 400 'Request Too Long' error is typically caused by a single corrupted or oversized cookie associated with the web service used to fetch the picture. Standard cache clearing often misses these specific service cookies, which is why a targeted deletion in your default web browser is required.

Open Browser Settings

Launch your default web browser (such as Microsoft Edge or Google Chrome) and click on the three-dot menu icon in the top right corner to open Settings.

Navigate to Cookie Management

Go to the Privacy and Security tab, then select 'Cookies and site data' or 'Manage and delete cookies and site data'.

Search for the Service Domain

Click on 'See all site data and permissions'. Use the search bar to find the specific domain of the service you were trying to use to insert the picture in Microsoft 365.

Delete Associated Cookies

Click the trash can icon or the 'Remove' button next to the relevant domain to delete its cookies. Restart your Microsoft 365 application and try inserting the picture again.

Delete Specific Site Cookies in Your Web Browser

Clear All Cookies as a Fallback: If you are unsure which specific service domain is causing the issue, you can safely choose to clear all cookies in your browser, though this will sign you out of most websites.

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Frequently Asked Questions

Why does the HTTP 400 Request Too Long error only happen when inserting pictures?

This error occurs because the external service handling the online picture search relies on your default browser's cookies. When one of these cookies becomes corrupted or excessively large, the server rejects the request header, resulting in the HTTP 400 error.

Will reinstalling Microsoft 365 fix the HTTP 400 error?

No, reinstalling Microsoft 365 typically does not resolve this specific issue. The error is caused by browser site data stored locally on your device, which remains unaffected by uninstalling or reinstalling the Office application suite.

Does clearing the standard browser cache fix the request too long error?

A standard cache clear might not resolve the issue if it does not explicitly target and delete the specific oversized cookies. You often need to manually search for and delete the site data associated with the image service you are using.

Microsoft Office Error Codes