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/16a25e8a0512a04ac3e07ff162d75541afb397dd/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-dGV4dD9peGxpYj1yYi00LjAuMCZ3PTk3MiZoPTM3OCZ0eHQ9JUUzJTgxJUFBJUUzJTgyJTkzJUUzJTgxJUE4JUUzJTgxJUFBJUUzJTgxJThGJTIwQ09SUyUyMCVFMyU4MSU4QyVFMyU4MiU4RiVFMyU4MSU4QiVFMyU4MiU4Qi4uLiVFMyU4MSVBRiVFMyU4MiU4MiVFMyU4MSU4NiVFNyVCNSU4MiVFMyU4MiU4RiVFMyU4MiU4QSVFMyU4MSVBQiVFMyU4MSU5OSVFMyU4MiU4QiVFMyU4MCU4MiZ0eHQtYWxpZ249bGVmdCUyQ3RvcCZ0eHQtY29sb3I9JTIzMjEyMTIxJnR4dC1mb250PUhpcmFnaW5vJTIwU2FucyUyMFc2JnR4dC1zaXplPTU2JnM9ZTI2M2ZhZmY4NGI2MzI3MThkY2IwYmY4ZDlmMWQ2MWU%26mark-x%3D142%26mark-y%3D57%26blend64%3DaHR0cHM6Ly9xaWl0YS11c2VyLWNvbnRlbnRzLmltZ2l4Lm5ldC9-dGV4dD9peGxpYj1yYi00LjAuMCZoPTc2Jnc9NzcwJnR4dD0lNDBhdHQ1NSZ0eHQtY29sb3I9JTIzMjEyMTIxJnR4dC1mb250PUhpcmFnaW5vJTIwU2FucyUyMFc2JnR4dC1zaXplPTM2JnR4dC1hbGlnbj1sZWZ0JTJDdG9wJnM9MzA1YTI2Yzc5MWZjNjQzNDAwOTkyNDRmZWUxZWRiYzk%26blend-x%3D142%26blend-y%3D486%26blend-mode%3Dnormal%26s%3D438a22eb17b4bdd083e92e4e07480901)