The Android Gradle plugin supports only Crashlytics Gradle plugin version 1.25.4 and higher. Project '***' is using version 1.25.1

The "Crashlytics Gradle plugin" is found in gradle in the io.fabric.tools:gradle package as mentioned on https://firebase.google.com/docs/crashlytics/get-started#android

You should find that in your projects root build.gradle file. Similar to this

buildscript {
    repositories {
        jcenter()
        google()
        maven { url 'https://maven.fabric.io/public' }
    }
    dependencies {
        classpath 'io.fabric.tools:gradle:1.25.1'
        ...
    }
}

allprojects {
    ...

Once you change it to classpath 'io.fabric.tools:gradle:1.25.4' that error should go away.

The versions of a maven dependency can also be found in its maven repository under

https://maven.fabric.io/public/io/fabric/tools/gradle/maven-metadata.xml

That trick should work for all maven repositories once you know the url:

<repo-base-url>/${groupId.replace('.','/')}/${artifactId}/maven-metadata.xml

You can also use a gradle plugin such as https://github.com/ben-manes/gradle-versions-plugin to have it lookup the latest versions in those maven-metadata.xml files for you.

If you simply want the latest you can also define the version with a wildcard, e.g.

classpath 'io.fabric.tools:gradle:1.+' // or even ...:gradle:+'

That would always give you the latest version that starts with 1.. It's rarely done in production since builds become less deterministic when dependency versions change from one moment to the next. But it's good to check whether gradle downloads a newer version.

Furthermore, Android Studio does check versions too, however you don't see the difference between there being no new version and when the check wasn't done yet. But when it did, you'll get an inspection hint and it can be quick fixed.