What it looks like
When Amazon Seller Central or the storefront returns a 400 Bad Request, the cause is almost always the same: tracking cookies grew too large for Amazon's request headers. Clearing all cookies fixes it but logs out every account in your browser. This extension surgically removes the tracking cookies and keeps your login intact.
HTTP 400 Bad Request Request Header Or Cookie Too Large
It happens to multi-account Amazon sellers, agencies switching between client accounts, and anyone who lives in Seller Central. Browser-level "Clear cookies" works, but it nukes every login on Amazon and forces 2FA again on every account. That is why this extension exists.
The extension reads every cookie on amazon.com and sellercentral.amazon.com, keeps the ones that hold your login, and deletes the rest.
Session tokens, identity cookies, and 2FA state are preserved. session-id, at-main, ubid-main, x-main, sst-main, JSESSIONID, and friends are explicitly protected.
Tracking, ad attribution, and analytics cookies that bloat your request headers get removed in seconds. That is what was triggering the 400 Bad Request.
One click shows what would be deleted without actually deleting anything. Useful when you are debugging or you just want to see what Amazon is dropping in your browser.
Three files: manifest.json, popup.html, popup.js. About 100 lines of commented JavaScript. Read it, audit it, modify it. No hidden background scripts, no remote calls.
The extension is unpacked, which means you load it directly from the folder. No Chrome Web Store review queue, no waiting.
Use the form below to get the download link. The zip is around 4 KB.
Chrome reads the extension from this folder every time the browser starts. Do not unzip it to Downloads or anywhere you might delete by accident.
Paste chrome://extensions into the address bar. Toggle "Developer mode" on in the top right.
Most users miss this step. The toggle is small and lives in the top-right corner of chrome://extensions.
Select the unzipped amazon-cookie-cleaner folder. The extension shows up in your toolbar.
The next time Amazon throws the 400 error, click the extension and click Clean Now. Refresh the page. Back in business.
Drop your email below. The download link arrives instantly. No spam, just the occasional note when a new free tool ships.
The Cookie Cleaner extension solves the error the moment you click it. But you can also prevent it from happening in the first place. We built this guide based on managing client Amazon accounts where this error was killing productivity. Start with Step 1 to fix it right now, then work through Steps 2-5 to prevent it from coming back. Steps 1-3 are the must-do core fix. Steps 4-5 are optional advanced tweaks for users who want to go further.
First, fix the immediate problem. The Cookie Cleaner extension surgically removes the tracking cookies causing the 400 error while keeping your login cookies intact. One click and you're back in business without re-logging into every Amazon account.
Scroll up and grab it from the form above (or jump down to the form below if you're still reading). Install it, click "Clean Now," and you'll be unblocked in under 30 seconds.
The remaining steps below prevent the error from coming back so you don't have to keep cleaning manually.
Most Amazon sellers have 5 to 15 browser extensions that touch Amazon (Helium 10, Keepa, Jungle Scout, RevSeller, Data Dive, DS Amazon Quick View, Camelizer, etc.). Each one writes its own cookies on every Amazon page load. Limiting them to run only when you click them eliminates the constant cookie growth.
chrome://extensions in a new tabYou'll still be able to use the extension on demand by clicking its icon. The extension just won't auto-run on every page.
If you sync Chrome across multiple devices and use Amazon on more than one, your sessions stack on each other. Disabling tab and history sync prevents this without breaking your password and bookmark sync.
chrome://settings/syncSetup/advanced in a new tabThis cuts off one of the silent sources of session stacking that contributes to cookie buildup.
Third-party cookies are the tracking and advertising cookies that pile up alongside your actual login cookies. Blocking them globally cuts the cookie load by 60% to 70% on most Amazon pages without affecting login or shopping functionality.
chrome://settings/cookies in a new tabThis is a global Chrome setting, not site-specific. Some sites legitimately need third-party cookies to function, particularly:
If a site you use breaks after enabling this setting, you have two options:
This is why this step is marked optional. The first three steps are the core fix and shouldn't break anything. This step has trade-offs you'll need to evaluate based on the sites you use.
Chrome has an experimental setting that enforces stricter cookie isolation between sites. Enabling it dramatically reduces cross-domain cookie pollution.
This setting lives at chrome://flags, which is Chrome's experimental features page. The "experimental" label is a real warning, not just bureaucratic boilerplate. Settings here can:
If something starts breaking on websites after you enable this, your first troubleshooting step should be to come back here and set it back to "Default."
chrome://flags in a new tabThis will close and reopen Chrome. Save your work first.
Step 1 fixes the error right now. Steps 2 and 3 are the core prevention. Steps 4 and 5 are optional advanced tweaks if you want to go further. If you haven't grabbed the extension yet, you can get it below.
Drop your email below. The download link arrives instantly. No spam, just the occasional note when a new free tool ships.
manifest.json are restricted to
*://*.amazon.com/. The extension cannot read or modify cookies on
any other site. Your bank, your email, your social accounts: untouched. The
manifest is in the zip if you want to verify.
manifest.json, popup.html, and popup.js.
No build step, no minification, no hidden background script. Read it, audit it,
modify it for your own use.
Drop your email. The extension lands in your inbox in seconds. Install once, use it whenever Amazon decides your headers are too long.
Send Me the Extension →