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+# Upgrade to node-fetch v2
+
+node-fetch v2 brings about many changes that increase the compliance of
+WHATWG's Fetch Standard. However, many of these changes meant that apps written
+for node-fetch v1 needs to be updated to work with node-fetch v2 and be
+conformant with the Fetch Standard.
+
+## `.text()` no longer tries to detect encoding
+
+Currently, `response.text()` attempts to guess the text encoding of the input
+material and decode it for the user. However, it runs counter to the Fetch
+Standard which demands `.text()` to always use UTF-8.
+
+In "response" to that, we have changed `.text()` to use UTF-8. A new function
+**`response.textConverted()`** is created that maintains the behavior of
+`.text()` last year.
+
+## Internal methods hidden
+
+Currently, the user can access internal methods such as `_clone()`,
+`_decode()`, and `_convert()` on the `response` object. While these methods
+should never have been used, node-fetch v2 makes these functions completely
+inaccessible, and may break your app.
+
+If you have a use case that requires these methods to be available, feel free
+to file an issue and we will be happy to help you solve the problem.
+
+## Headers
+
+The `Headers` class has gotten a lot of updates to make it spec-compliant.
+
+```js
+//////////////////////////////////////////////////////////////////////////////
+// If you are using an object as the initializer, all arrays will be reduced
+// to a string.
+const headers = new Headers({
+  'Abc': 'string',
+  'Multi': [ 'header1', 'header2' ]
+});
+
+// before                             after
+headers.get('Multi') =>               headers.get('Multi') =>
+  'header1';                            'header1,header2';
+headers.getAll('Multi') =>            headers.getAll('Multi') =>
+  [ 'header1', 'header2' ];             [ 'header1,header2' ];
+
+// Instead, to preserve the older behavior, you can use the header pair array
+// syntax.
+const headers = new Headers([
+  [ 'Abc', 'string' ],
+  [ 'Multi', 'header1' ],
+  [ 'Multi', 'header2' ]
+]);
+
+
+//////////////////////////////////////////////////////////////////////////////
+// All method parameters are now stringified.
+const headers = new Headers();
+headers.set('null-header', null);
+headers.set('undefined', undefined);
+
+// before                             after
+headers.get('null-header')            headers.get('null-header')
+  => null                               => 'null'
+headers.get(undefined)                headers.get(undefined)
+  => throws                             => 'undefined'
+
+
+//////////////////////////////////////////////////////////////////////////////
+// Invalid HTTP header names and values are now rejected outright.
+const headers = new Headers();
+headers.set('Héy', 'ok');          // now throws
+headers.get('Héy');                // now throws
+new Headers({ 'Héy': 'ok' });      // now throws
+```
+
+## 0.10.x support dropped
+
+If you are still using Node.js v0.10, upgrade ASAP. Not only has Node.js
+dropped support for that release branch, it has become too much work for us to
+maintain. Therefore, we have dropped official support for v0.10 (it may still
+work but don't expect them to do so).