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tom93 · tom93 · commit 2e0a1ae8e5a4 · 2023-02-08T09:34:24.000+13:00
diff --git a/README.md b/README.md
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+# URL Redirection Service
+
+This is a simple web page that redirects to the URL encoded in the URI fragment (the part after the "#").
+For example <https://tom93.github.io/redirect/#https://example.com> redirects to <https://example.com>.
+It is useful for preventing "intelligent" software from processing URLs of a particular form.
+
+The target URL can be encoded using `encodeURIComponent()`.
+Alternatively, the following function preserves most special characters for readability while still producing a valid encoding:
+
+```js
+function encodeURIFragment(s) {
+  /* Encode a string for inclusion in the URL fragment. */
+  /*
+    Relevant syntax specification (https://www.rfc-editor.org/rfc/rfc3986.html):
+    fragment      = *( pchar / "/" / "?" )
+    pchar         = unreserved / pct-encoded / sub-delims / ":" / "@"
+    unreserved    = ALPHA / DIGIT / "-" / "." / "_" / "~"
+    sub-delims    = "!" / "$" / "&" / "'" / "(" / ")"
+    / "*" / "+" / "," / ";" / "="
+
+    The set of safe characters is almost the same as for encodeURI(), except encodeURI() does not encode "#".
+    So we just use encodeURI() and then encode "#" manually.
+  */
+  return encodeURI(s).replace(/#/g, "%23");
+}
+```
diff --git a/docs/index.html b/docs/index.html
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+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width,initial-scale=1">
+    <link rel="icon" href="data:,">
+    <title>Redirecting...</title>
+    <style>body { font-family: sans-serif; }</style>
+  </head>
+  <body>
+    <div id="message"></div>
+    <script>
+      var url = decodeURIComponent(location.hash.substring(1));
+      if (!url) {
+        document.getElementById("message").textContent = "Error: No URL specified";
+      } else if (!/^http[s]?:\/\//.test(url)) {
+        document.getElementById("message").textContent = "Error: Invalid URL";
+      } else {
+        location.href = url;
+      }
+    </script>
+  </body>
+</html>
