TL;DR
A transaction signature (tx sig) is the unique identifier for every Solana transaction — a base-58 encoded string you can use to look up any transaction on a block explorer.
Every Solana transaction produces a unique signature when signed by the sender’s private key. This signature serves as both authentication (proving the sender authorized the transaction) and a unique identifier. It looks like a long string of characters: e.g., “5U3Ld7...”. No two transactions can have the same signature. It’s the receipt for your on-chain activity.
After executing a trade, your wallet or bot returns the transaction signature. Paste it into Solscan, Solana Explorer, or SolanaFM to see: whether the transaction succeeded or failed, the exact token amounts swapped, fees paid, all instructions executed, and the accounts involved. This is essential for debugging failed trades, verifying payment amounts, and understanding exactly what happened in complex DeFi transactions.
If a transaction shows as “failed,” you still paid the base fee but no state changes occurred (your tokens are safe). Common failure reasons: insufficient SOL for fees, slippage exceeded your tolerance, compute budget exceeded, or the pool state changed between simulation and execution. Failed transactions are harmless but cost a tiny base fee. Check the error message in the explorer for the specific failure reason.