Technical Deep Dive

January 22, 20266 min read

Client-Side vs Server-Side Randomness: Which Is More Trustworthy?

When you spin a wheel online, where does the "random" actually happen? The answer determines whether you can truly trust the result.

The short answer: Client-side randomness (in your browser) is more transparent because you can verify it. Server-side randomness requires trusting the website operator. For public giveaways where trust matters, client-side is the gold standard.

Understanding the Difference

Client-Side

Runs in your browser

Random number generated on your device
No network request needed
Verifiable via browser dev tools
Website cannot manipulate result

Server-Side

Runs on remote server

Random number generated elsewhere
Requires network request
Cannot verify what happens on server
Requires trust in operator

Why Location Matters

The fundamental question is: who controls the randomness?

Client-Side = Transparency

When randomness happens in your browser, you can literally watch it happen. Open your browser's developer tools, check the Network tab, and verify that no data is sent when you click "spin." The selection is happening right on your device.

Server-Side = Black Box

When randomness happens on a server, you're trusting that the server is honest. You send a request, and the server tells you who won. But you have no way to verify what actually happened. The server could be using manipulated selection.

How Each Approach Works

Client-Side Flow

Click Spin

→

Browser generates random

→

Winner selected locally

No network activity. Everything happens on your device.

Server-Side Flow

Click Spin

→

Request sent to server

→

Server returns winner

You must trust the server. No way to verify what happened.

When Server-Side Makes Sense

Server-side randomness isn't always bad. There are legitimate use cases:

Regulated Gambling

Casinos use audited server-side systems with regulatory oversight. Third-party auditors verify fairness.

Blockchain Verification

Some systems publish random seeds to blockchain before selection, allowing post-hoc verification.

Commit-Reveal Schemes

Server commits to a random value (publishes hash) before selection, then reveals it after.

Multi-Party Computation

Multiple independent servers contribute to randomness, so no single party can manipulate.

However, most free online wheel spinners don't implement these safeguards. For typical giveaways and classroom use, client-side is simpler and more trustworthy.

How to Check If a Tool Uses Client-Side Selection

Open Developer Tools

Press F12 or right-click → Inspect

Go to Network Tab

Click the 'Network' tab in dev tools

Clear the Log

Click the clear button (🚫) to start fresh

Spin the Wheel

Click the spin button on the website

Check for Requests

If no new requests appear, it's client-side

Red Flag: "Our Servers Ensure Fairness"

Be skeptical of tools that claim server-side selection is "more secure" or "more fair." Without third-party auditing or cryptographic proofs, server-side selection is simply less transparent. For most use cases, client-side with cryptographic randomness is the better choice.

AllWheel's Approach

All AllWheel tools use 100% client-side selection:

No Server Requests

Selection happens entirely in your browser

Web Crypto API

Cryptographically secure randomness from your OS

Verifiable

Check Network tab yourself—zero requests during spin

Works Offline

Once loaded, works without internet connection

Experience Transparent Selection

Try our client-side wheel spinner. Open dev tools and verify for yourself.

Try Wheel Spinner →

Frequently Asked Questions

Is client-side randomness truly random?

Yes, when using the Web Crypto API. It accesses your operating system's cryptographically secure random number generator, which gathers entropy from hardware sources. It's the same quality of randomness used for encryption.

Can't someone modify the JavaScript?

A user could modify their own browser's JavaScript, but they'd only be "cheating" themselves. For giveaways, the host runs the selection on their device—participants can't modify the host's browser.

Why do some sites use server-side?

Sometimes for legitimate reasons (regulated gambling, blockchain verification). But often it's simply because the developers didn't consider transparency, or because they want to collect data about selections.

How do I prove my giveaway was fair?

Use a client-side tool and screen record the entire process, including showing the Network tab is empty. Read our complete guide on how to prove a giveaway was fair.

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