Changes to Redirects with query string parameters are coming

Features Updates
,
35

For anyone struggling with this issue, here’s an edge function that fixes the problem. It detects the Netlify query string redirect behavior by comparing incoming request and outgoing response query params on 301s and 302s, and strips the query string the location header value if the parameters are identical.

We didn’t want this behavior at all, so this works for us, but you might want to add a filter to this logic to conditionally apply this behavior based on specific paths.

Finally, beware that you will only be able to test this behavior when running on Netlify CDN. Dev environment does not exhibit the behavior.

/* 
Netlify automatically appends origin query parameters to 
all redirected URLs if a query string is not present in the redirected URL
This handler fixes it by removing the query string from the redirected URL if the parameters are identical

*/

export default async (request, context) => {
    try{
        
        const url = new URL(request.url);
        if(!url.search) return;

        console.log(`Incoming URL: ${request.url}`);

        let res = await context.next();
        
        console.log(res.status);

        if([301,302].includes(res.status)){
            const location = res.headers.get('location'),
                redirectedQueryString = location?.slice(location.indexOf('?'));

            console.log(`Redirected URL: ${location}`);

            if(redirectedQueryString){

                const params = new URLSearchParams(redirectedQueryString);

                // Compare incoming and outgoing query parameters
                let identical = true;
                for(const [key, value] of url.searchParams.entries()){
                    if(params.get(key) !== value){
                        console.log(`Incoming and redirected query params are different: ${key}=${value} vs ${params.get(key)}`);
                        identical = false;
                        break;
                    }
                }

                if(identical){
                    console.log("Found identical query strings, stripping the redirect URL query string");
                    res.headers.set('location', location.split('?')[0]);
                    return res;
                }else{
                    console.log("Incoming and redirected query params are different, not altering location");
                }

            }
        }
        
    }catch(err){
        console.error(err);
    }
    
}
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