Pages, styles and blocking

Read or change a loaded page

from browse import on

@on.page_load(match="*://example.com/*")
async def comfortable_reading(page):
    await page.inject_css("body { line-height: 1.7; }")
    title = await page.eval("document.title")
    print(title)

Page scripts share the document with the website but run in the extension’s isolated JavaScript world. They do not share the page’s JavaScript variables or other extensions’ worlds. If a page navigates outside your permitted sites during evaluation, Browse withholds the result.

Register styles for future loads

from browse import styles

style_id = styles.register(
    "*://news.ycombinator.com/*",
    css="body { background: #fff0f6 !important; }",
    run_at="start",
)
# Later: styles.unregister(style_id)

styles.register accepts a match pattern or list, css and/or js, and run_at="start" or "end". Registration can happen at import time. unregister stops future injections; pages already showing the style keep it until reloaded. There is a limit of 100 registrations per extension. Styles and page scripts apply to the main frame only.

Exchange messages with a page

from browse import on, styles

styles.register(
    "*://example.com/*",
    js="""
        browse.onMessage(value => console.log(value));
        browse.postMessage({title: document.title});
    """,
    run_at="end",
)

@on.message(match="*://example.com/*")
async def received(message, page):
    print(message)
    await page.post({"received": True})

Block resources or hide elements

from browse import rules

rules.block("*.doubleclick.net", types=["script", "image"], on=["example.com"])
rules.hide(".cookie-banner", on=["example.com"])
# Remove this extension's registered rules: rules.clear()

Blocking rules are applied by the browser’s content blocker without calling Python for each resource. Use host patterns for blocked hosts and on sites. Hiding needs pages permission for the affected sites; omitting on applies everywhere and requires broad permission.

Resource types are document, image, style-sheet, script, font, raw, svg-document, media and popup. Omit types to cover all supported types. Each extension can register up to 500 rules.

• Events and navigation
• Manifest and permissions