files/en-us/web/api/document/open/index.md
{{APIRef("DOM")}}
The Document.open() method opens a document for
{{domxref("Document.write", "writing", "", "1")}}.
This does come with some side effects. For example:
open()
None.
A Document object instance.
The following simple code opens the document and replaces its content with a number of different HTML fragments, before closing it again.
document.open();
document.write("<p>Hello world!</p>");
document.write("<p>I am a fish</p>");
document.write("<p>The number is 42</p>");
document.close();
An automatic document.open() call happens when
{{domxref("document.write()")}} is called after the page has loaded.
This method is subject to the same same-origin policy as other properties, and does not work if doing so would change the document's origin.
There is a lesser-known and little-used three-argument version of
document.open(), which is an alias of {{domxref("Window.open()")}} (see
its page for full details).
This call, for example opens github.com in a new window, with its opener set to
null:
document.open("https://www.github.com", "", "noopener=true");
Browsers used to support a two-argument document.open(), with the
following signature:
document.open(type, replace);
Where type specified the MIME type of the data you are writing (e.g.
text/html) and replace if set (i.e., a string of "replace")
specified that the history entry for the new document would replace the current history
entry of the document being written to.
This form is now obsolete; it won't throw an error, but instead just forwards to
document.open() (i.e., is the equivalent of just running it with no
arguments). The history-replacement behavior now always happens.
{{Specifications}}
{{Compat}}