location <YOUR_LOCATION> {
if ($request_method = 'OPTIONS') {
add_header 'Access-Control-Allow-Origin' '*';
add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
# Custom headers and headers various browsers *should* be OK with but aren't
add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range';
# Tell client that this pre-flight info is valid for 20 days
add_header 'Access-Control-Max-Age' 1728000;
add_header 'Content-Type' 'text/plain; charset=utf-8';
add_header 'Content-Length' 0;
return 204;
if ($request_method = 'POST') {
add_header 'Access-Control-Allow-Origin' '*';
add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range';
add_header 'Access-Control-Expose-Headers' 'Content-Length,Content-Range';
if ($request_method = 'GET') {
add_header 'Access-Control-Allow-Origin' '*';
add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range';
add_header 'Access-Control-Expose-Headers' 'Content-Length,Content-Range';
If you use Amazon S3 with Label Studio, see Troubleshoot CORS and access problems.
If you use Google Cloud Storage with Label Studio, see Troubleshoot CORS and access problems.
If you serve your data from an HTTP server created like follows: python -m http.server 8081 -d, run the following from the command line:
npm install http-server -g
http-server -p 3000 --cors
Not every host supports CORS setup, but you can to try locate CORS settings in the admin area of your host configuration.
Import HTML data for more.
If you want to correct existing annotations, you can minify your source HTML files in the same way that Label Studio does. The minification is performed with the following script:
import htmlmin
with open("sample.html", "r") as f:
html_doc = f.read()
minified_html_doc = htmlmin.minify(html_doc, remove_all_empty_space=True)
If minification does not seem to be affecting the offset placements, complex CSS or other reasons could be the cause.
Troubleshoot pre-annotations to investigate possible reasons why predictions don’t show up.
Label Studio playground.
