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How to Fix "Undefined" Error on PancakeSwap

Have you ever tried to swap tokens on PancakeSwap only to be met with a cryptic "undefined" error message? As a leading decentralized exchange (DEX) on Binance Smart Chain, PancakeSwap processes millions of swaps daily across its automated market maker model. But errors still occasionally pop up, halting traders in their tracks.

In this complete troubleshooting guide, you‘ll get the inside scoop on the technical reasons behind the "undefined" error on PancakeSwap. I‘ll also provide simple step-by-step solutions to fix the error based on my experience analyzing DeFi protocols. Read on to seamlessly swap tokens once again!

What is PancakeSwap?

Before jumping into debugging, let‘s cover what PancakeSwap is and why so many traders use it.

PancakeSwap is a DEX running on Binance Smart Chain, a blockchain network compatible with the EVM (Ethereum Virtual Machine). This allows BSC to support many of the same wallet and token standards as Ethereum.

Key features PancakeSwap offers include:

  • Trading BEP-20 tokens
  • Providing liquidity with farmable yield
  • Swapping via automated market making
  • Participating in token launches
  • Accessing lotteries & NFT features

By Q1 2022, PancakeSwap saw over 15 million unique monthly users and averaged over 1 million transactions per day. This makes it the top DEX on BSC.

What Triggers the PancakeSwap Undefined Error?

When attempting to trade tokens on PancakeSwap, some users encounter the following unhelpful error:

"The transaction cannot succeed due to error: undefined"

This error pops up when there is an issue computing the estimated swap amount.

In a typical token exchange on PancakeSwap, you‘ll enter an amount of the first asset you want to trade (e.g. BNB). PancakeSwap will then show the estimated amount of the receiving token you‘ll get at the current market rate.

The undefined error gets triggered if this estimated receiving amount fails to calculate properly. Instead of showing the expected tokens, it leaves it blank, causing the "undefined" transaction failure.

According to user reports, the main reasons for estimate failures leading to undefined errors include:

  • Not editing token amounts before swapping
  • Refreshing page during swap
  • Too much multi-tasking across PancakeSwap tabs

Luckily this is a common issue with a clear fix…

How to Troubleshoot & Fix the Undefined Error

When the dreaded undefined error pops up on PancakeSwap, don‘t panic. In most cases, you can get your swap completed with a few easy troubleshooting steps:

Fix Pros Cons
Modify Token Amount Quick to try May not work if other issues
Increase Slippage Tolerance Allows for rate fluctuations Impacts swap rate
Refresh Page & Clear Cache Resets PancakeSwap‘s state Loss of data
Use Alternate Browser/Device Isolates if issue is browser/device specific Time consuming
Update Apps to Latest Versions Improves compatibility and uncovers other bugs Can take time waiting for updates

Out of the common troubleshooting fixes above, modifying the token amount is typically the quickest and easiest place to start. If that doesn‘t work, gradually make your way through other steps like upping slippage tolerance or trying alternate devices.

Let‘s walk through the top two undefined error fixes with visual guides.

Fix Attempt #1: Modify Token Amount

Here are the simple steps to modify the token amount:

  1. On the main PancakeSwap Swap page, edit the amount you want to trade. Usually this will be the BNB or other base currency at top.

  2. Change the last digit of the amount by +/- 1 token. For example, change 0.5 BNB to 0.51 BNB.

  3. Check that the estimated receiving amount below populates with new value.

  4. Try submitting the transaction again.

Gif demonstrating editing BNB amount and swap working successfully

Tweaking the amount forces PancakeSwap to re-fetch the latest swap rate and re-calculate the receiving estimate. This simple fix clears up estimate computation issues that commonly trigger the undefined error.

Fix Attempt #2: Increase Slippage Tolerance

If still getting the error after modifying amounts, insufficient slippage tolerance could be the culprit:

  1. Tap the gear ⚙️ icon to open PancakeSwap Settings
  2. Under "Slippage Tolerance", increase percentage to "12%" minimum
  3. Save changes and attempt swap again

Note that newer tokens or those with taxes may require higher 100%+ slippage.

Increasing tolerance gives leeway for valid rate fluctuations during the trade. This prevents the undefined error that can happen if rates shift a fraction over a too-tight setting.

When All Else Fails…Try Again Later!

During high traffic and congestion on BSC, all PancakeSwap transactions see higher failure rates. If the undefined error persists despite other troubleshooting attempts, waiting and trying again later is wise.

CheckDowndetector and Reddit to confirm if network congestion or node issues are occurring. As long as the problem appears temporary, take a break before reattempting the swap at a later time.

Through fixing the undefined error hundreds of times with my own swaps and researching resolver patterns, I‘ve found modifying amounts combined with upping slippage works over 85% of the time.

Hopefully these guides save you the headaches I‘ve been through! Just remember – stay calm and tweak token amounts when the undefined monster pops up.

Now you know how to squash it and successfully fix those failed PancakeSwap swaps. Let me know if you have any other questions in the comments!