WebDriver

As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.

Conformance requirements phrased as algorithms or specific steps may be implemented in any manner, so long as the end result is equivalent. Algorithms in this document are typically written with readability, rather than performance, in mind.

In equations, all numbers are integers, addition is represented by “+”, subtraction by “−”, division by “÷”, and bitwise OR by “|”. The characters “(” and “)” are used to provide logical grouping in these contexts.

The mathematical function min(value, value[, value]) returns the smallest item of two or more values. Conversely, the function max(value, value[, value]) returns the largest item of two or more values.

The mathematical function floor(value) produces the largest integer, closest to positive infinity, that is not larger than value.

A Universally Unique Identifier (UUID) is a 128 bits long URN that requires no central registration process. Generating a UUID means Creating a UUID From Truly Random or Pseudo-Random Numbers, and converting it to the string representation. [RFC4122]

The Unix Epoch is a value that approximates the number of seconds that have elapsed since the Epoch, as described by The Open Group Base Specifications Issue 7 section 4.15 (IEEE Std 1003.1).

An integer is a Number that is unchanged under the ToInteger operation.

The initial value of an ECMAScript property is the value defined by the platform for that property, i.e. the value it would have in the absence of any shadowing by content script.

The browser chrome is a non-normative term to refer to the representation through which the user interacts with the user agent itself, as distinct from the accessed web content. Examples of browser chrome elements include, but are not limited to, toolbars (such as the bookmark toolbar), menus (such as the file or context menu), buttons (such as the back and forward buttons), door hangers (such as security and certificate indicators), and decorations (such as operating system widget borders).

The webdriver-active flag is set to true when the user agent is under remote control. It is initially false.

WebIDLinterface mixin NavigatorAutomationInformation {
  readonly attribute boolean webdriver;
};
Navigator includes NavigatorAutomationInformation;

webdriver

Returns true if webdriver-active flag is set, false otherwise.

It is acknowledged that this is complementary to the Evil Bit [RFC3514].

The WebDriver protocol consists of communication between:

Local end

The local end represents the client side of the protocol, which is usually in the form of language-specific libraries providing an API on top of the WebDriver protocol. This specification does not place any restrictions on the details of those libraries above the level of the wire protocol.

Remote end

The remote end hosts the server side of the protocol. Defining the behavior of a remote end in response to the WebDriver protocol forms the largest part of this specification.

For remote ends the standard defines two broad conformance classes, known as node types:

Intermediary node

Intermediary nodes are those that act as proxies, implementing both the local end and remote end of the protocol. However they are not expected to implement remote end steps directly. Nodes between a specific intermediary node and an endpoint node are said to be upstream of the endpoint node.

Endpoint node

An endpoint node is the final remote end in a chain of nodes that is not an intermediary node. The endpoint node is implemented by a user agent or a similar program.

All remote end node types must be black-box indistinguishable from a remote end, from the point of view of local end, and so are bound by the requirements on a remote end in terms of the wire protocol.

The readiness state of a remote end indicates whether it is free to accept new connections. It must be false if the implementation is an endpoint node and the list of active HTTP sessions is not empty, or otherwise if the remote end is known to be in a state in which attempting to create new sessions would fail. In all other cases it must be true.

If the intermediary node is a multiplexer that manages multiple endpoint nodes, this might indicate its ability to purvey more sessions, for example if it has hit its maximum capacity.

WebDriver remote ends must provide an HTTP compliant wire protocol where the endpoints map to different commands.

As this standard only defines the remote end protocol, it puts no demands to how local ends should be implemented. Local ends are only expected to be compatible to the extent that they can speak the remote end's protocol; no requirements are made upon their exposed user-facing API.