← Glossary / Akamai Sensor Data Block

What is Akamai Sensor Data Block?

An Akamai sensor data block occurs when Akamai Bot Manager (BMP) intercepts a request because the client failed to provide valid, human-like telemetry. This telemetry—collected via heavily obfuscated JavaScript and submitted in the _abck cookie or a POST payload—includes mouse movements, keystroke dynamics, and deep hardware fingerprints. For scraping pipelines, triggering this block means your execution environment has been mathematically proven to be non-human.

Anti-BotAkamai BMPTelemetryJavaScript ExecutionFingerprinting
// 02 — definitions

Failing the
telemetry test.

Akamai doesn't just look at your headers. It measures how your browser behaves, renders, and interacts before granting access.

Ask a DataFlirt engineer →

TL;DR

Akamai Bot Manager injects a script that monitors hundreds of client-side signals, compiling them into a 'sensor data' payload. If your scraper cannot execute this script, or if the generated data reveals a headless environment, Akamai issues a 403 Forbidden or a silent challenge loop. Bypassing it requires a flawless browser execution environment.

01Definition & structure
An Akamai sensor data block is a defensive action taken by Akamai Bot Manager when a client fails to prove it is human. The proof is delivered via "sensor data"—a heavily obfuscated payload of telemetry collected by an injected JavaScript file. This payload includes:
  • Hardware fingerprints (Canvas, WebGL, Audio context)
  • Browser environment variables (navigator properties, screen dimensions)
  • Behavioral biometrics (mouse movements, touch events, keystrokes)
If this data is missing, malformed, or indicative of automation, the request is blocked.
02How it works in practice
When you request an Akamai-protected page, the server returns the HTML along with an injected script and an initial _abck cookie. The script executes, gathers telemetry, and POSTs the sensor data back to a specific Akamai endpoint. Akamai evaluates the payload; if it passes, the _abck cookie is updated to a "valid" state, allowing subsequent API or HTML requests to succeed. If it fails, you are trapped in a challenge loop or served a 403 Forbidden.
03The signals Akamai tracks
The sensor script is notoriously thorough. It checks for the presence of cdc_adoQpoasnfa76pfcZLmcfl_ (a classic ChromeDriver artifact), verifies that the WebGL renderer matches the expected OS, and measures the exact timing between DOM events. It even tracks how the mouse moves—perfectly straight lines or instant teleportation between elements will immediately flag the session as a bot.
04How DataFlirt handles it
We do not attempt to reverse-engineer the sensor payload. Instead, DataFlirt routes requests through our proprietary browser fleet, which runs unmodified, headed Chrome on real residential hardware. We inject human-like behavioral patterns (scrolls, mouse curves) at the OS level, allowing the Akamai script to execute naturally and generate a mathematically flawless sensor payload.
05The silent tarpit
Akamai doesn't always issue a hard 403 when sensor data fails. Often, it employs a "tarpit" strategy: it returns a 200 OK, but the response body contains nothing but the challenge script again. Naive scrapers will continuously execute the script, fail the evaluation, and receive the script again, burning compute resources in an infinite loop without ever reaching the target data.
// 03 — the telemetry model

How Akamai scores
your sensor data.

Akamai evaluates the sensor payload across multiple dimensions: hardware consistency, behavioral biometrics, and network coherence. DataFlirt monitors these exact vectors to maintain pipeline access.

Hardware Coherence = C = WebGL_vendor ⊕ Canvas_hash ⊕ User_Agent
Mismatches between claimed OS and actual rendering hardware result in an instant block. Akamai BMP heuristics
Behavioral Entropy = H(b) = Σ mouse_velocity × click_variance
Zero interaction or perfectly linear mouse movements flag the session as automated. Client-side telemetry analysis
DataFlirt Telemetry Pass Rate = P = valid_abck_cookies / total_sessions
Maintained at > 99.2% across our fleet by using real hardware environments. Internal SLO
// 04 — the sensor exchange

A failed sensor
data submission.

A trace of a Puppeteer script attempting to bypass Akamai BMP. The script executes the JS, but the resulting sensor data leaks its headless nature.

Akamai BMPPuppeteer403 Forbidden
edge.dataflirt.io — live
CAPTURED
// Initial GET request
GET /api/inventory HTTP/2
Response: 202 Accepted (Challenge injected)
Set-Cookie: _abck=...~0~...

// Client executes Akamai JS
Executing: /149e9513-01fa-4fb0-aad4-566afd725d1b/2d206a39-8ed7-437e-a3be-862e0f06eea3/fp

// Sensor data generation
sensor.webdriver: true // Puppeteer leak
sensor.mouse_events: 0 // No interaction

// POSTing sensor data
POST /_sec/cp_challenge/ak-challenge-2-0.htm
Payload: {"sensor_data": "2.02,-1,100,..."}

// Akamai evaluation
Akamai-Bot-Score: 98 (Malicious Bot)
Response: 403 Forbidden
Pipeline Status: BLOCKED
// 05 — detection vectors

What triggers a
sensor data block.

Akamai's sensor script looks for inconsistencies between what your headers claim and what your JavaScript environment actually proves. These are the most common failure points.

SAMPLE SIZE ·  ·  ·  ·    1.2M blocks
WINDOW ·  ·  ·  ·  ·  ·   30d trailing
UPDATED ·  ·  ·  ·  ·  ·  2026-05-19
01

Headless browser leaks

94% of blocks · navigator.webdriver, missing plugins, CDP artifacts
02

Missing behavioral data

82% of blocks · No mouse movements, zero scroll events, instant execution
03

Hardware/Header mismatch

75% of blocks · Linux GPU rendering with a Windows User-Agent
04

Invalid _abck cookie

60% of blocks · Failed JS execution or malformed payload submission
05

Stale sensor data

45% of blocks · Reusing old payloads across multiple sessions
// 06 — our stack

Valid telemetry,

generated natively on real hardware.

You cannot reverse-engineer and fake Akamai sensor data at scale—the obfuscation changes too frequently and the math is too complex. DataFlirt bypasses Akamai by actually running the sensor script in a pristine, headed browser environment on real residential hardware. We don't spoof the telemetry; we generate it legitimately, ensuring the _abck cookie is always valid and the bot score remains low.

Akamai Session State

Live telemetry validation for an active session on an Akamai-protected target.

cookie._abck valid · ~-1~
cookie.bm_sz present
execution.env headed Chrome
hardware.profile macOS · M2
behavioral.input human-like curves
tls.fingerprint matches User-Agent
pipeline.status active

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// 07 — FAQ

Common
questions.

Common questions about Akamai sensor data, the _abck cookie, and how to maintain access to heavily protected targets.

Ask us directly →
What is the _abck cookie? +
The _abck cookie is Akamai's primary telemetry tracking mechanism. When you first visit a site, you receive a baseline _abck cookie (often ending in ~0~). After the client-side JavaScript executes and POSTs the sensor data, Akamai validates it and updates the cookie (often to ~-1~ or similar), granting access to the protected endpoints.
Can I just copy the _abck cookie from my browser to my scraper? +
No. The _abck cookie is cryptographically tied to your IP address, your TLS fingerprint (JA3/JA4), and your specific browser session. It also expires quickly. Replaying a cookie from a different environment will result in an immediate block.
Why does my Playwright script fail even with stealth plugins? +
Stealth plugins patch basic leaks like navigator.webdriver, but Akamai's sensor script checks deep JavaScript runtime properties, canvas rendering quirks, and behavioral biometrics that stealth plugins miss. If your mouse movements are synthetic or your GPU doesn't match your OS, Akamai will flag the sensor data.
How often does Akamai update its sensor script? +
Constantly. Akamai frequently pushes updates to the obfuscated JavaScript that generates the sensor data. This is why attempting to reverse-engineer the script and generate the payload via pure Python/Go is a losing battle—it breaks every time the script changes.
How does DataFlirt maintain access to Akamai-protected targets? +
We don't emulate or reverse-engineer the sensor data. We run the actual Akamai script inside real, headed browsers deployed on residential hardware. Because the environment is genuinely human-like, the sensor data generated is mathematically valid, keeping our bot scores below the blocking threshold.
What is the difference between a sensor data block and a reference number error? +
A reference number error (e.g., "Access Denied - Reference #18...") is a generic block page often triggered by WAF rules, IP reputation, or rate limiting. A sensor data block specifically means the Bot Manager evaluated your client-side telemetry and determined you are an automated script.
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// 08 — keep reading

Related glossary terms

Anti-Scraping

Akamai Bot Manager

The overarching anti-bot system that deploys the sensor data challenge.

Read →
Anti-Scraping

Akamai Reference Number Error

The generic block page served when Akamai denies access to a request.

Read →
Anti-Bot Bypass

Browser Fingerprinting

The technique used by sensor scripts to identify your hardware and software stack.

Read →
Anti-Bot Bypass

JavaScript Challenge

The mechanism of forcing a client to execute code before granting access.

Read →