How Arbitrage Scanners Compare Exchange Prices
An arbitrage scanner compares cryptocurrency prices across different exchanges to identify potential price differences. Instead of manually opening several exchanges and checking the same trading pair, the scanner collects market data, compares the prices, and highlights differences that may be worth investigating.
The basic idea is simple:
Find the same asset → compare its prices across exchanges → identify the difference → check whether the difference is actually usable.
However, the price shown by a scanner is only the starting point. Trading fees, liquidity, slippage, and changing market conditions can affect the actual outcome.
How Exchange Price Comparison Works
Suppose an arbitrage scanner monitors three exchanges and finds the following price for ETH/USDT:
| Exchange | ETH Price |
| Exchange A | $4,000 |
| Exchange B | $4,025 |
| Exchange C | $4,060 |
The scanner can identify Exchange A as the lower-priced market and Exchange C as the higher-priced market.
The apparent difference is:
$4,060 − $4,000 = $60
This creates a potential cross-exchange arbitrage opportunity.
But the scanner does not simply assume that the $60 difference is profit. The next step is determining whether those prices are actually available and whether the costs of executing the trade leave a meaningful margin.
What Data Does the Scanner Compare?
A scanner may compare several pieces of market information depending on how it is designed.
These can include:
- Trading pair prices
- Bid prices
- Ask prices
- Order-book data
- Trading volume
- Available liquidity
- Exchange fees
- Market movements
The most useful comparison is generally based on prices at which a trader could potentially execute rather than relying only on the last traded price.
For example, if one exchange shows a last traded price of $4,000 but its current ask price is $4,020, buying at $4,000 may not actually be possible.
This is why current market data matters when evaluating an opportunity.
You can read more about this in Why Arbitrage Scanners Need Real-Time Data.
A Simple Beginner Workflow
If you're new to arbitrage scanners, the comparison process can be understood in six steps:
1. Select the exchanges
Choose the exchanges you want the scanner to monitor.
2. Select a trading pair
For example:
BTC/USDT
3. Collect current prices
The scanner receives market information from the selected exchanges.
4. Compare the prices
It identifies where the asset is relatively cheaper and where it is relatively more expensive.
5. Calculate the apparent spread
For example:
Buy price: $100,000
Sell price: $100,700
Gross difference: $700
6. Check whether the opportunity is practical
Before acting, consider fees, liquidity, slippage, transfer costs, and execution speed.
The important lesson is that price comparison comes before profit calculation.
How the Scanner Finds the Cheapest and Most Expensive Market
Imagine the scanner receives these prices for BTC:
- Exchange A: $100,200
- Exchange B: $100,450
- Exchange C: $99,950
- Exchange D: $100,600
The scanner can sort the available prices and identify:
Lowest observed price: $99,950
Highest observed price: $100,600
The apparent difference is:
$650
The scanner can then flag this difference for further analysis.
This process becomes increasingly useful when monitoring many exchanges and trading pairs because manually comparing every market would take considerably more time.
Why the Displayed Spread Can Be Misleading
A price difference does not automatically mean that the entire spread can be captured.
Suppose a scanner shows:
Buy: $10,000
Sell: $10,200
The displayed difference is $200, or 2%.
But imagine that the order book only has a small amount available at $10,000.
If you attempt to purchase a larger position, part of your order may execute at $10,050, $10,080, or higher.
At the same time, the selling side could move lower.
Your actual spread could therefore be much smaller than the scanner initially displayed.
This is known as slippage.
The Role of Liquidity
Liquidity determines how much of an asset can potentially be bought or sold without significantly affecting its price.
Consider two opportunities:
Opportunity A
Displayed spread: 1%
High liquidity
Opportunity B
Displayed spread: 2%
Low liquidity
The second opportunity has the larger displayed spread, but that does not necessarily make it more practical.
If there is insufficient liquidity to execute the desired order, the actual execution prices may be considerably different from the prices initially displayed.
This is why a scanner should be used alongside liquidity and order-book analysis.
How Fees Affect the Comparison
The scanner may identify a large price difference, but trading fees can reduce the available margin.
For example:
Buy price: $4,000
Sell price: $4,040
Gross difference: $40
If the combined trading costs are $25, only $15 remains before considering other costs.
That is why traders should distinguish between:
Gross spread and Net arbitrage profit
For a deeper explanation, see How to Calculate Net Arbitrage Profit With a Scanner.
What Happens After the Scanner Finds a Difference?
Once a potential difference is detected, the scanner has done its primary job.
The next step is evaluation.
A trader can check:
- Is the price difference still available?
- Is there enough liquidity?
- What are the trading fees?
- How much slippage is expected?
- Are there transfer or network costs?
- Can the trades be executed quickly enough?
- Does the opportunity remain after all costs?
Only after these questions have been considered can the price difference be evaluated properly.
Manual Comparison vs Scanner Comparison
Without a scanner, a trader might need to:
- Open Exchange A.
- Check the asset price.
- Open Exchange B.
- Check the same asset.
- Open Exchange C.
- Compare all the numbers.
- Repeat the process for another trading pair.
This becomes increasingly difficult as the number of exchanges and assets grows.
A scanner centralizes this comparison process.
Instead of manually searching for differences, the trader can start with a list of detected opportunities and investigate the ones that meet their criteria.
For beginners, understanding How to Use an Arbitrage Scanner for Multiple Exchanges is a useful next step.
How Real-Time Comparison Helps
Crypto prices can change quickly.
An opportunity that exists at one moment may disappear shortly afterward as buyers and sellers react to the market.
This means a scanner needs sufficiently fresh data to make its comparisons useful.
The faster the market moves, the more important it becomes to distinguish between a current price difference and an outdated one.
However, even real-time data does not guarantee execution at the displayed prices.
Conclusion
Arbitrage scanners compare exchange prices by collecting market data, matching trading pairs, and identifying differences between available markets.
The process can be summarized simply:
Collect prices → Compare markets → Find the spread → Check liquidity → Calculate costs → Evaluate the opportunity.
The displayed spread is only the beginning. Fees, slippage, liquidity, transfer costs, and changing prices all influence whether an apparent difference can actually be captured.
For traders who want to monitor cryptocurrency price differences across supported markets, PokoBit provides an arbitrage-focused platform for discovering potential opportunities.