How To Fix 400 Bad Request Error

Last Update: March 30, 2019

Just a real quick one today. I read a blog or question yesterday in regard to a member having the same problem as I was and how to fix 400 bad request error which was occurring on our sites.

I can't for the life of me find the question again to respond on it but I wanted to say a huge thank you to Marion Black for her suggestion on that post and share with you what worked for me.

Edit: Thanks again to Marion for providing the link to the original blog from Gordon - check it out here:

I run Thrive on my sites but there was another member who wasn't and was having the same bad request error, so it's not just Thrive and seems like it can be any theme.

After following Marion's suggestion I started disabling and removing plugins to see what didn't play well with my theme and site architecture.

As it turns out I believe it is a clash between the Classic Editor plugin and some themes.

After removing Classic Editor yesterday I have had no more bad error requests on either of the two sites. My third site which I had not downloaded Classic Editor on never had the bad request errors occurring.

So once again thank you Marion for your speedy suggestion, it seems to have fixed my problem, and hopefully others who have this same error may find this blog and can try this fix for themselves.

Edit: Well after a few days the bad request error is back on my MMO niche, but doesn't seem to be affecting the niche site. So this isn't the be all and end all fix I was hoping.

Back to the drawing board with Site Support!

Edit #2: Thanks to Gosa I have now banished the bad request and have access to my site. Try this: click on the lock in the URL that brings up the bad request, clear cookies and bad request disappears. How simpe is that!! Give it a try guys and see how you go.

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Avecita Premium
Hi All, I'm also getting this on a brand new site. Site Support couldn't help me and blamed my computer, but its clearly not as it seems loads of us are having this issue of late. I have tried the flushing the DNS cache suggesting, deleting cookies and history and also the one mentioned at the end of this post, clicking the lock on the URL and erasing cookies, but t no avail. Any more suggestions? And also, anyone any idea WHY this is happening?
tbowyer Premium
Hi Heidi.

A 404 is a failure to find a resource (for instance, a web page, or an image or some such). The first thing to think about is a broken link: are you certain that all your links still work? Did you rename something? Did you move anything?

Just double check that what is supposed to be there *actually is*. If it is and you're certain of that, maybe give me a PM shout and I'll see if I can lend a hand. If I it turns out that I can't, at least we can sit down (metaphorically) on a stone cold floor and weep bitter tears together. 😉 Misery loves company, n'est pas?

Harryallen1 Premium
Nice one I have the same I’ll check it out thanks
alisterbrede Premium
Thanks for the info. It is much appreciated.
kmer6 Premium
Thank you for sharing this important information.
chender684 Premium
was this a 403 request error after upgrading to 5.1?
HeidiY Premium
No Curtis, I had installed the Classic Editor at some point well after upgrading to 5.1.

This all seemed to start out of the blue, both sites had been functioning perfectly fine with the Classic Editor installed but all of a sudden the bad request error started showing up.
LKick Premium
Great to hear. Trial and error sometimes is the only way. Glad it worked and we all appreciate Marion for helping. Love WA community just for people like Marion and you Heidi. Linda
HeidiY Premium
Thank you Linda, I am not good with technical stuff at all so to find such an easy fix was a real relief.

Hopefully my blog and Gordon's (the original question) will help out others if they find themselves in the same situation.
JWhite5 Premium
Thanks for sharing,Heidi!
MarionBlack Premium
Thanks for the shout out. Here's the link to the original question if you'd like to add it to your post
HeidiY Premium
Very much appreciated Marion, I was going to tackle Site Support this weekend when I had enough time to try and fix this, but so far *touchwood* it all seems to be resolved.

Thanks for the link also, I have edited the blog to include it.
Eliz65 Premium
Thanks Heidi and Marion... I was having the same issue. Hopefully this solves my issue too!
HeidiY Premium
Be great if you can drop back and let us know. I hope it works for you too.
Calh60 Premium
Thanks for sharing Heidi and thank you Marion.

Barney44 Premium
The actual things you experienced as your tried removing plugin might be an interesting topic for a length post. Being able to understand what each plugin does with regards to all the others to me is intriguing.

Thanks Heidi for sharing.

HeidiY Premium
It was only the Classic Editor I actually remove on both sites, and while I was going I disabled WP Clone but didn't actually delete it as I do use it occassionally.

Most of my other plugins are part of the Thrive Architecture on both these sites.

The MMO site but I run Sumo, Pretty Links, GDPR Cookie Consent & Blog2Social.

I do run a heap of others on my niche site (hangover from before I upgraded) and I didn't disable or remove any of those. I run Sumo, Blog2Social, WP Product Review, GDPR Cookie Consent, Shortcodes Ultimate, Tablepress, and probably others LOL. I really do need to do a clean up of that site.

Actually pretty boring as nothing happened except the bad request error has not occurred since.
CandP Premium
Good to know, thanks Heidi.
Colette and Philip
FKelso Premium
Good one -- glad you found out.
SaraStorey Premium
That's good to know, Thank you!
RuthlynB Premium
I am so glad you found the solutions to your problem and I do love Marion Black she is my go-to person when I have a problem.
HeidiY Premium
She is an absolute gem Ruthlyn.

I have lost count of the times Marion has helped me, she is a wealth of knowledge and we are very fortunate to have her that is for sure.