Access to XMLHttpRequest at 'http://localhost:8081' from origin 'http://localhost:8080' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: It does not have HTTP ok status. Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:8080' is ther
![なんとなく CORS がわかる...はもう終わりにする。 - Qiita](https://cdn-ak-scissors.b.st-hatena.com/image/square/870c3b1650ee6ad4a84b3cd1a5887c8d9f59c5b8/height=288;version=1;width=512/https%3A%2F%2Fqiita-user-contents.imgix.net%2Fhttps%253A%252F%252Fcdn.qiita.com%252Fassets%252Fpublic%252Farticle-ogp-background-412672c5f0600ab9a64263b751f1bc81.png%3Fixlib%3Drb-4.0.0%26w%3D1200%26mark64%3DaHR0cHM6Ly9xaWl0YS11c2VyLWNvbnRlbnRzLmltZ2l4Lm5ldC9-dGV4dD9peGxpYj1yYi00LjAuMCZ3PTk3MiZoPTM3OCZ0eHQ9JUUzJTgxJUFBJUUzJTgyJTkzJUUzJTgxJUE4JUUzJTgxJUFBJUUzJTgxJThGJTIwQ09SUyUyMCVFMyU4MSU4QyVFMyU4MiU4RiVFMyU4MSU4QiVFMyU4MiU4Qi4uLiVFMyU4MSVBRiVFMyU4MiU4MiVFMyU4MSU4NiVFNyVCNSU4MiVFMyU4MiU4RiVFMyU4MiU4QSVFMyU4MSVBQiVFMyU4MSU5OSVFMyU4MiU4QiVFMyU4MCU4MiZ0eHQtYWxpZ249bGVmdCUyQ3RvcCZ0eHQtY29sb3I9JTIzMUUyMTIxJnR4dC1mb250PUhpcmFnaW5vJTIwU2FucyUyMFc2JnR4dC1zaXplPTU2JnM9ODliYThiMWU4OWMxNTY1ZGNlMWRkNmVhYTc0OTlkODU%26mark-x%3D142%26mark-y%3D57%26blend64%3DaHR0cHM6Ly9xaWl0YS11c2VyLWNvbnRlbnRzLmltZ2l4Lm5ldC9-dGV4dD9peGxpYj1yYi00LjAuMCZoPTc2Jnc9NzcwJnR4dD0lNDBhdHQ1NSZ0eHQtY29sb3I9JTIzMUUyMTIxJnR4dC1mb250PUhpcmFnaW5vJTIwU2FucyUyMFc2JnR4dC1zaXplPTM2JnR4dC1hbGlnbj1sZWZ0JTJDdG9wJnM9OTRlZmFiZjIyNjQ3ZDI4MWVhOTdkY2M1ZWJiZjliMzU%26blend-x%3D142%26blend-y%3D486%26blend-mode%3Dnormal%26s%3Db2c7be1930e0c12637936aa9b12c8b25)