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Used to create a button, that can be assigned arbitrary click() events. The label (value) of the button can be used as an input or set via the output of a function.


As input: passes the button value as a str into the function

As output: expects a str to be returned from a function, which is set as the label of the button


Parameter Description

str | Callable

default: "Run"

Default text for the button to display. If callable, the function will be called whenever the app loads to set the initial value of the component.


float | None

default: None

If value is a callable, run the function 'every' number of seconds while the client connection is open. Has no effect otherwise. Queue must be enabled. The event can be accessed (e.g. to cancel it) via this component's .load_event attribute.


Literal['primary', 'secondary', 'stop']

default: "secondary"

'primary' for main call-to-action, 'secondary' for a more subdued style, 'stop' for a stop button.


Literal['sm', 'lg'] | None

default: None

Size of the button. Can be "sm" or "lg".


str | None

default: None

URL or path to the icon file to display within the button. If None, no icon will be displayed. Must be within the working directory of the Gradio app or an external URL.


str | None

default: None

URL to open when the button is clicked. If None, no link will be used.



default: True

If False, component will be hidden.



default: True

If False, the Button will be in a disabled state.


str | None

default: None

An optional string that is assigned as the id of this component in the HTML DOM. Can be used for targeting CSS styles.


list[str] | str | None

default: None

An optional list of strings that are assigned as the classes of this component in the HTML DOM. Can be used for targeting CSS styles.



default: True

If False, component will not render be rendered in the Blocks context. Should be used if the intention is to assign event listeners now but render the component later.


int | None

default: None

relative width compared to adjacent Components in a Row. For example, if Component A has scale=2, and Component B has scale=1, A will be twice as wide as B. Should be an integer.


int | None

default: None

minimum pixel width, will wrap if not sufficient screen space to satisfy this value. If a certain scale value results in this Component being narrower than min_width, the min_width parameter will be respected first.


Class Interface String Shortcut Initialization



Uses default values



Uses default values



Uses default values



Uses default values



Uses default values


import gradio as gr
import os

def combine(a, b):
    return a + " " + b

def mirror(x):
    return x

with gr.Blocks() as demo:

    txt = gr.Textbox(label="Input", lines=2)
    txt_2 = gr.Textbox(label="Input 2")
    txt_3 = gr.Textbox(value="", label="Output")
    btn = gr.Button(value="Submit")
    btn.click(combine, inputs=[txt, txt_2], outputs=[txt_3])

    with gr.Row():
        im = gr.Image()
        im_2 = gr.Image()

    btn = gr.Button(value="Mirror Image")
    btn.click(mirror, inputs=[im], outputs=[im_2])

    gr.Markdown("## Text Examples")
        [["hi", "Adam"], ["hello", "Eve"]],
        [txt, txt_2],
    gr.Markdown("## Image Examples")
        examples=[os.path.join(os.path.dirname(__file__), "lion.jpg")],

if __name__ == "__main__":

Event Listeners


Event listeners allow you to capture and respond to user interactions with the UI components you've defined in a Gradio Blocks app. When a user interacts with an element, such as changing a slider value or uploading an image, a function is called.

Supported Event Listeners

The Button component supports the following event listeners. Each event listener takes the same parameters, which are listed in the Event Arguments table below.

Listener Description

gradio.Button.click(fn, ···)

Triggered when the Button is clicked.

Event Arguments

Parameter Description

Callable | None | Literal['decorator']

default: "decorator"

the function to call when this event is triggered. Often a machine learning model's prediction function. Each parameter of the function corresponds to one input component, and the function should return a single value or a tuple of values, with each element in the tuple corresponding to one output component.


Component | list[Component] | set[Component] | None

default: None

List of gradio.components to use as inputs. If the function takes no inputs, this should be an empty list.


Component | list[Component] | None

default: None

List of gradio.components to use as outputs. If the function returns no outputs, this should be an empty list.


str | None | Literal[False]

default: None

defines how the endpoint appears in the API docs. Can be a string, None, or False. If set to a string, the endpoint will be exposed in the API docs with the given name. If None (default), the name of the function will be used as the API endpoint. If False, the endpoint will not be exposed in the API docs and downstream apps (including those that gr.load this app) will not be able to use this event.



default: False

If True, will scroll to output component on completion


Literal['full', 'minimal', 'hidden']

default: "full"

If True, will show progress animation while pending


bool | None

default: None

If True, will place the request on the queue, if the queue has been enabled. If False, will not put this event on the queue, even if the queue has been enabled. If None, will use the queue setting of the gradio app.



default: False

If True, then the function should process a batch of inputs, meaning that it should accept a list of input values for each parameter. The lists should be of equal length (and be up to length max_batch_size). The function is then required to return a tuple of lists (even if there is only 1 output component), with each list in the tuple corresponding to one output component.



default: 4

Maximum number of inputs to batch together if this is called from the queue (only relevant if batch=True)



default: True

If False, will not run preprocessing of component data before running 'fn' (e.g. leaving it as a base64 string if this method is called with the Image component).



default: True

If False, will not run postprocessing of component data before returning 'fn' output to the browser.


dict[str, Any] | list[dict[str, Any]] | None

default: None

A list of other events to cancel when this listener is triggered. For example, setting cancels=[click_event] will cancel the click_event, where click_event is the return value of another components .click method. Functions that have not yet run (or generators that are iterating) will be cancelled, but functions that are currently running will be allowed to finish.


float | None

default: None

Run this event 'every' number of seconds while the client connection is open. Interpreted in seconds. Queue must be enabled.


Literal['once', 'multiple', 'always_last'] | None

default: None

If "once" (default for all events except .change()) would not allow any submissions while an event is pending. If set to "multiple", unlimited submissions are allowed while pending, and "always_last" (default for .change() event) would allow a second submission after the pending event is complete.


str | None

default: None

Optional frontend js method to run before running 'fn'. Input arguments for js method are values of 'inputs' and 'outputs', return should be a list of values for output components.


int | None | Literal['default']

default: "default"

If set, this this is the maximum number of this event that can be running simultaneously. Can be set to None to mean no concurrency_limit (any number of this event can be running simultaneously). Set to "default" to use the default concurrency limit (defined by the default_concurrency_limit parameter in Blocks.queue(), which itself is 1 by default).


str | None

default: None

If set, this is the id of the concurrency group. Events with the same concurrency_id will be limited by the lowest set concurrency_limit.