difference between playwright, cypress and selenium

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1️⃣ Cypress Architecture Overview

Unlike Selenium or Playwright:

• Cypress runs inside the browser itself (or in the same Node process that controls the browser).
• It injects its automation code directly into the web page via a JavaScript bundle.
• Cypress does not use WebDriver, and it rarely talks to the browser engine via a protocol like CDP.

Diagrammatically:

Your Test Code (Cypress) 
       │
       ▼
Cypress Test Runner (Node + Browser bundle)
       │
       ▼
Browser DOM / JS
       │
       ▼
Native events / page interactions

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2️⃣ How Cypress Click Works Internally

When you do:

cy.get('#login-button').click()

Cypress does:

1. Find the element in the DOM (it’s actually running inside the browser context).

2. Scroll element into view.

3. Dispatch native events using JavaScript, not CDP:

   • mousedown, mouseup, click, focus

4. Ensure application stability before and after the click (waits for animations, XHR, promises, etc.)

Essentially:

element.dispatchEvent(new MouseEvent('mousedown', { bubbles: true, clientX: 200, clientY: 150 }));
element.dispatchEvent(new MouseEvent('mouseup', { bubbles: true, clientX: 200, clientY: 150 }));
element.dispatchEvent(new MouseEvent('click', { bubbles: true, clientX: 200, clientY: 150 }));

✅ Notice: There is no separate driver or CDP command involved. Cypress is literally controlling the DOM from inside the browser.

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3️⃣ Comparison with Selenium / Playwright

Feature	Selenium	Playwright	Cypress
Driver needed	Yes (chromedriver/geckodriver)	No	No
Protocol	W3C WebDriver → driver → CDP	Direct CDP / native protocol	None; runs in-browser JS
Low-level action	Input.dispatchMouseEvent (via driver)	Input.dispatchMouseEvent (direct)	element.dispatchEvent in JS
Access to browser internals	Limited	Full via CDP	Limited to what can be done via JS
Auto-wait / retry	Manual waits or built-in (Playwright has auto-wait better)	Built-in waits, retries, stability checks	Built-in waits, retries, and DOM stability

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4️⃣ Key Takeaways

• Selenium: W3C command → driver → CDP → browser
• Playwright: Direct CDP → browser
• Cypress: Runs inside the browser → dispatches DOM events via JavaScript

So yes, all three eventually trigger the same browser behavior (click, type, navigate), but the path and control mechanism differ:

• Selenium → external driver
• Playwright → direct low-level protocol
• Cypress → internal JS automation

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5️⃣ Analogy

Analogy	Selenium	Playwright	Cypress
Click a button	Ask your assistant to press the button	Press it yourself via a direct wire to the robot	You reach in and press the button yourself

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💡 Extra: This is why Cypress cannot control multiple browsers simultaneously, or run remote sessions natively — it’s limited to the browser it’s injected into. Playwright and Selenium can do that because they use external processes/protocols.

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