“Screenshot API for Kotlin” can mean four different jobs: capturing the current Android device screen in a test, rendering one view or Compose node, detecting that a user took a screenshot, or sending a website URL to a hosted renderer. This guide starts with the official AndroidX test capture, then covers Android 14 detection and remote website screenshots so you can choose the API that matches your outcome.
How do I take a screenshot in Kotlin?
For an instrumentation or debugging test that needs the whole visible device screen, AndroidX provides the experimental takeScreenshot() function. It returns a Bitmap and is documented for debugging scenarios, not as a production end-user screenshot feature.
Minimal AndroidX instrumentation example
import androidx.test.core.app.takeScreenshot
import org.junit.Test
class ScreenshotTest {
@Test
fun captureCurrentDeviceScreen() {
val bitmap = takeScreenshot()
// Inspect the Bitmap, save it, or pass it to a test helper.
}
}The function is in the androidx.test:core artifact. Add the AndroidX test core dependency that matches the rest of your test stack, and call it from an instrumentation/test context where UiAutomation is available.
Important constraints
takeScreenshot()is experimental; opt in if your Kotlin and dependency versions require an experimental-API annotation.- Do not call it on the main thread. Main-thread use is documented to throw
IllegalStateException. - It is not safe for concurrent calls. Serialize screenshot operations in your test suite.
- A UiAutomation capture failure can surface as a
RuntimeException; treat that as an environment or capture failure rather than a bad assertion. - The implementation forces the app’s root views to redraw and handles disabled hardware rendering to improve stability.
This gives you a bitmap of the device screen at the time of capture. It does not upload the image, create a PDF, or provide a user-facing sharing flow; those are separate responsibilities you must implement.
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How do I capture an Android screen in an instrumentation test?
Use whole-device capture only when the test really needs the complete screen, including system bars or multiple views. For visual validation of one widget, AndroidX recommends a targeted capture instead.
Capture only the view or Compose node under test
For a classic View, use the targeted capture API named by the AndroidX reference (such as captureToBitmap). For Jetpack Compose, use the corresponding node image API (such as captureToImage). These approaches reduce unrelated pixels and make golden-image comparisons less fragile. The exact helper and test rule depend on the AndroidX testing libraries and Compose version in your project, so keep the API version aligned with your build.
A reliable test sequence
- Launch the Activity and wait for the UI state you intend to verify.
- Perform all taps, text entry, navigation, and synchronization before capture.
- Run the capture off the main thread and ensure no other test is capturing concurrently.
- Write the returned
Bitmapto your test artifact directory or pass it directly to an image assertion. - On failure, retain the bitmap and the test log so the visual difference can be inspected.
Saving a Bitmap in a test helper
import android.graphics.Bitmap
import java.io.File
import java.io.FileOutputStream
fun Bitmap.writePng(file: File) {
file.parentFile?.mkdirs()
FileOutputStream(file).use { output ->
compress(Bitmap.CompressFormat.PNG, 100, output)
}
}Call bitmap.writePng(...) from your test’s artifact-writing code. PNG is lossless and usually preferable for pixel assertions; JPEG introduces compression differences.
How do I detect when a user takes a screenshot?
Android 14 introduced a privacy-preserving screenshot detection API. It reports that a supported user screenshot occurred while a particular Activity was visible, but it does not provide the image. Detection and capture are therefore different operations.
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Register and unregister with the Activity lifecycle
private val screenCaptureCallback = Activity.ScreenCaptureCallback {
// Respond to the event. The screenshot image is not provided.
}
override fun onStart() {
super.onStart()
registerScreenCaptureCallback(mainExecutor, screenCaptureCallback)
}
override fun onStop() {
super.onStop()
unregisterScreenCaptureCallback(screenCaptureCallback)
}Declare the permission in the manifest:
<uses-permission android:name="android.permission.DETECT_SCREEN_CAPTURE" />Register while the Activity is started and unregister when it stops. The system displays a notice for each detection signal, so explain in your UI why your app reacts (for example, offering a copy-link action or warning about sensitive data).
What this callback does not detect
The documented signal covers the specified hardware-button screenshot combination. It does not report screenshots made with ADB commands or instrumentation tests that capture the current screen. If your requirement is to stop content from appearing in screenshots, use the documented FLAG_SECURE window protection. That is a capture restriction, not an event detector.
Which Kotlin screenshot approach should I choose?
| Goal | API or service | Result | Execution and constraints |
|---|---|---|---|
| Debug or assert the complete Android screen | AndroidX takeScreenshot() |
Bitmap |
Instrumentation/test context; experimental; never main thread; no concurrent calls |
| Assert one View or Compose node | Targeted capture such as captureToBitmap or captureToImage |
Image of the selected UI | Best for focused visual validation; API availability follows your AndroidX/Compose versions |
| Know that a user captured the Activity | Android 14 ScreenCaptureCallback |
Event only, no image | Activity lifecycle registration and DETECT_SCREEN_CAPTURE permission |
| Render a website URL | Hosted or self-hosted screenshot service | PNG, JPEG, WebP, or PDF, depending on service | External endpoint, authentication, network and page-rendering behavior |
How do I capture a website screenshot from Kotlin?
A website screenshot service renders a remote URL in a browser environment; it does not capture your Android app’s current screen. One vendor, Screenshot API, lists an “Official” Kotlin SDK for Android, Ktor, and Spring Boot with implementation 'org.screenshot-api:kotlin-sdk:1.0.0'. Treat that coordinate and version as a vendor claim: verify that the artifact is available and current in your repository before making it a production dependency. The vendor also says its REST API can be called from any language, which lets Kotlin applications avoid SDK coupling.
A self-hosted Kotlin/Ktor option
The separate screenshottech/screenshot-api GitHub project describes a Kotlin/Ktor screenshot-generation service. Its README gives ./gradlew run as a local start command, documents Docker startup options, and shows a POST /api/v1/screenshots request with an API key. It claims PNG, JPEG, WEBP, and PDF output plus full-page and viewport capture. These are project documentation claims, and this project is not established as related to the vendor SDK above; do not mix their package names, endpoints, or authentication instructions.
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Calling a REST endpoint from Kotlin with Ktor
import io.ktor.client.HttpClient
import io.ktor.client.request.forms.submitForm
import io.ktor.http.Parameters
suspend fun requestWebsiteScreenshot(
client: HttpClient,
endpoint: String,
apiKey: String,
pageUrl: String
): ByteArray {
return client.submitForm(
url = endpoint,
formParameters = Parameters.build {
append("api_key", apiKey)
append("url", pageUrl)
}
).readBytes()
}Adapt parameter names, authentication, output selection, and response handling to the service you actually deploy. Keep API keys on a server rather than shipping them in an Android APK. Set connection and request timeouts, validate the target URL, and impose a response-size limit before writing bytes to storage.
Or skip the browser setup
ScreenshotNeo is a hosted website screenshot API and MCP server. It accepts a URL and returns PNG, JPEG, WebP, or PDF without requiring you to operate a browser farm. Its clean-shot workflow accepts cookie or consent banners before capture and removes more than 60 known consent platforms, newsletter popups, and chat widgets; each step can be turned off. Bot checks or CAPTCHAs, blank pages, timeouts, failed loads, and cache hits are not billed, and response headers identify the page verdict and billing status.
From Kotlin, the simplest integration is an HTTP GET. See the ScreenshotNeo API documentation for the current parameters.
import java.net.URI
import java.net.http.HttpClient
import java.net.http.HttpRequest
import java.net.http.HttpResponse
import java.nio.file.Files
import java.nio.file.Path
fun main() {
val apiKey = System.getenv("SCREENSHOTNEO_API_KEY")
?: error("Set SCREENSHOTNEO_API_KEY")
val target = "https://stripe.com"
val requestUri = URI.create(
"https://api.screenshotneo.com/v1/shot" +
"?access_key=$apiKey&url=" +
java.net.URLEncoder.encode(target, Charsets.UTF_8)
)
val request = HttpRequest.newBuilder(requestUri).GET().build()
val response = HttpClient.newHttpClient().send(
request,
HttpResponse.BodyHandlers.ofByteArray()
)
require(response.statusCode() in 200..299) {
"Screenshot request failed: ${response.statusCode()}"
}
Files.write(Path.of("shot.webp"), response.body())
}ScreenshotNeo also supports full-page capture with lazy images loaded, CSS-selector element capture, dark mode, 12 device presets or custom viewports, retina scale, PDF paper size/margins/orientation/page ranges, custom CSS and JavaScript, pre-capture clicks, hidden selectors, waits for a selector/delay/network idle, ad/tracker/request/resource blocking, custom headers/cookies/user agents/Authorization, timezone and geolocation, transparent backgrounds, image resizing, configurable-TTL caching, signed links, asynchronous jobs with signed webhooks, bulk capture of up to 100 URLs per call, a usage API, an OpenAPI specification, and compatibility with parameter names used by other screenshot APIs. Its MCP server exposes take_screenshot, get_page_info, and capture_pdf for Claude, Cursor, and other MCP clients.
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Troubleshooting Kotlin screenshot captures
IllegalStateException from AndroidX capture
Move the call off the main thread and ensure the test is running with instrumentation support. A main-thread call is a documented failure mode.
Intermittent or corrupted images
Serialize calls, wait for the UI to reach a deterministic state, and avoid capturing during transitions or animations. Whole-screen capture triggers a redraw, so allow pending layout work to settle before asserting pixels.
Screenshot callback never fires
Check that the device is running Android 14 or later, the manifest contains DETECT_SCREEN_CAPTURE, registration occurs in onStart(), and unregistration occurs in onStop(). The callback will not report ADB or instrumentation captures.
Remote service returns an error or HTML instead of an image
Verify the endpoint, authentication, URL encoding, timeout, and response content type. Keep secrets server-side, log status and provider headers, and check whether the target page blocks automation or requires cookies, headers, geolocation, or a longer wait.
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SDK dependency cannot be resolved
Re-check the vendor’s repository, group ID, artifact ID, and version. The listed org.screenshot-api:kotlin-sdk:1.0.0 coordinate is vendor documentation, not a guarantee that your configured repositories still serve it.
Performance, reliability, and security notes
- Capture the smallest useful surface: a node or view is cheaper to compare and less sensitive to unrelated layout changes than a full device image.
- Use PNG for exact visual assertions and JPEG/WebP when transfer size matters more than lossless pixels.
- For website rendering, define explicit waits and viewport/device settings; otherwise asynchronous fonts, images, consent dialogs, and responsive breakpoints can change output.
- Cache only when the page’s freshness requirements allow it. For authenticated pages, protect cookies, Authorization headers, signed links, and generated files as secrets.
- Never place a hosted-service API key in an Android client distributed to users. Proxy requests through a controlled backend and apply URL allow-lists where users can submit targets.
Frequently Asked Questions
Can AndroidX takeScreenshot be used in a released app?
It is documented for instrumentation and debugging contexts. It is not presented as a production end-user screenshot or screen-recording mechanism.
Does Android screenshot detection give me the captured bitmap?
No. Android 14’s callback reports a supported screenshot event only; the image is not exposed.
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Are Screenshot API’s Kotlin SDK and screenshottech/screenshot-api the same project?
No relationship is established. They are separate vendor and repository claims with different installation and endpoint details.
What should I use for a website screenshot pipeline in Kotlin?
Use a hosted REST API when you do not want to run browser infrastructure; use a self-hosted Ktor service when you need to operate the renderer yourself. Keep credentials and rendering policy on a server.
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