Solscan.io<\/a>, locate the transaction using its signature\u2014a 88-character base58 string that uniquely identifies it. Once the transaction page loads, the interface displays several sections: an overview with the transaction fee and status, a list of account keys accessed, instruction details, and a logs panel. The overview immediately shows whether the transaction succeeded or failed; a red indicator means the transaction landed but at least one instruction reversed.<\/p>\nThe accounts section lists every account touched during execution, organized as read-only or writable. This matters because program logic often depends on which accounts were provided and whether they could be modified. A developer debugging a “missing required account” error can cross-reference the accounts section against the program’s expected inputs. If a required signer is missing, it appears in the list but without the “S” designation indicating a signature. If a required writable account is provided as read-only, the mismatch becomes visible here.<\/p>\n
Below the accounts section, Solscan displays the instruction sequence. Each instruction shows its program ID, number of accounts passed to it, and a breakdown of which accounts were used. For native Solana programs like the token program or system program, Solscan decodes the instruction and displays the human-readable operation\u2014”Transfer 1000000 tokens from source to destination,” for example. For user-deployed programs, the instruction appears as raw bytes unless Solscan has a cached IDL (Interface Definition Language) file that describes the program’s expected inputs.<\/p>\n
The logs section occupies the lower portion of the page and can be expanded to full-screen view. This is where program logs, system messages, and error codes appear in chronological order. The logs are searchable and can be filtered by source program address or message type.<\/p>\n
Understanding instruction indices and call stacks<\/h2>\n
When a transaction contains multiple instructions, each one has an index starting at zero. If a transaction invokes the system program to create an account at instruction zero, then transfers tokens at instruction one, and fails when calling a custom program at instruction two, the logs clearly mark which instruction produced which output. This index is critical for isolating the failure point.<\/p>\n
CPIs (cross-program invocations) add another layer of complexity. When program A calls program B, the call appears in the logs with a slightly indented format or marked with a depth indicator. Nested calls\u2014program B invoking program C\u2014show further indentation. By reading the structure of these nested calls, a developer can reconstruct the execution flow and identify exactly where execution halted. A common failure pattern is an instruction that partially completes (modifying accounts, consuming computation), then fails during a nested CPI. The logs show the partial progress, allowing the developer to understand why the transaction consumed fees despite not finishing.<\/p>\n
The runtime also logs the amount of computation consumed at various points. Solana transactions have a fixed computation budget (typically 200,000 units for standard transactions). If a program runs out of compute before finishing, it returns an “out of memory” or “execution limit exceeded” error. The logs show how much compute was consumed at each instruction, allowing a developer to identify bottlenecks. A single instruction consuming 150,000 units leaves little room for subsequent instructions; if the transaction fails with a compute budget exceeded error, the culprit is often visible in the logged compute consumption.<\/p>\n
Error propagation also appears in the call stack. If a nested program returns an error, the calling program receives it as a return value. If the calling program does not check this return value and continues as if the call succeeded, downstream errors become confusing. By reading the logs, a developer can see the exact point where an error occurred and whether calling programs properly handled it or ignored it.<\/p>\n
Decoding common error messages and failure patterns<\/h2>\n
Solana’s runtime produces standardized error codes that appear in transaction logs. Error Code 1<\/strong> (Program failed to complete successfully) is a catch-all that means the program explicitly returned an error, often accompanied by a program-specific error code. Error Code 2<\/strong> (Program panicked) indicates the program hit an unexpected condition, usually a failed assertion or unwrap statement. Error Code 3<\/strong> (Program executed an illegal instruction) points to the program attempting an operation it should not perform, such as modifying a read-only account.<\/p>\nWhen a program panics, the logs usually show the file and line number where the panic occurred, provided the program was compiled with debug symbols. This is invaluable for pointing directly to the source code that failed. A “range check failed” panic message indicates array access out of bounds. A “integer overflow” panic suggests an arithmetic operation that exceeded capacity. By matching the panic message to the program source, a developer can identify the exact line and reason for failure.<\/p>\n
Account-related failures are among the most common. “Account not found” means the account was not included in the transaction. “Invalid owner” means the account is owned by the wrong program (the token program owns token accounts, the system program owns most other accounts; a mismatch causes this error). “Insufficient funds” means an account does not have enough tokens to transfer. These errors appear in the logs with the account’s address, allowing the developer to verify they provided the correct account.<\/p>\n
Signature verification failures occur when a required signer did not actually sign the transaction. The logs show which account’s signature was missing or invalid. This is distinct from “account not provided”: the account is present but not marked as signed, or the signature does not match the account’s public key. A developer debugging this error should verify that the signing wallet actually signed the transaction and that the account address in the transaction matches the wallet’s public key.<\/p>\n
Instruction parsing errors indicate the program received data it could not deserialize into the expected format. This often happens when a frontend application constructs instruction data incorrectly, misaligning the data layout or providing the wrong number of bytes. The logs show the program and sometimes the instruction discriminator (a unique identifier for the instruction type), allowing a developer to verify the instruction type matches and that data was passed in the correct order.<\/p>\n
Using logs to trace state changes and verify program behavior<\/h2>\n
Beyond error diagnosis, logs reveal program state changes that may not be immediately visible from account balances alone. A program can be designed to log balance updates, permission changes, or state transitions as they occur. By reading these logs, a developer can verify that the program behaved as intended. If a token transfer is supposed to happen but the balance does not change, the logs might show why: the transfer succeeded, but a subsequent check failed and the transaction reversed; or the transfer never executed because an earlier instruction failed.<\/p>\n
State changes also involve account data modifications that do not always appear in the transaction’s explicit account changes. A program might store data in a PDA (Program Derived Account) managed by the program itself. By reading logs that document these changes, a developer can trace the program’s internal state. For instance, a DeFi protocol might log every state update to its global configuration account. By following the logs, a developer can confirm the state transitions were correct and identify any skipped steps.<\/p>\n
Logs also make explicit the order of operations. In concurrent systems, order matters. A program might be designed to deposit tokens, then update a balance counter, then emit a log. If the logs show the balance counter updated before the deposit, or the deposit never happened, the program has a logic error. By comparing the actual order shown in logs to the intended order in the source code, a developer can spot subtle bugs that would not cause a runtime error but still produce wrong results.<\/p>\n
Advanced debugging techniques with Solscan’s log analysis<\/h2>\n
For complex transactions involving multiple programs, Solscan’s full-screen log view becomes essential. The search feature allows filtering logs by text or program address. A developer troubleshooting a specific program can search its address to see only logs it produced, filtering out noise from system programs and other contracts. This isolation is particularly valuable in multi-step transactions where dozens of log entries might appear.<\/p>\n
Comparing successful and failed transactions side-by-side in separate browser tabs reveals differences in instruction execution or log output. If one transaction succeeds and another fails, the developer can read the logs from both and spot where they diverge. The successful transaction’s log sequence shows the intended path; the failed one reveals where execution halted or took a different branch.<\/p>\n
For developer tools and smart contract verification, understanding logs is foundational. When deploying a new program, developers often test it with simplified versions that log heavily at each step. By reading the logs, they confirm the program follows the intended logic. Once in production, selective logging (avoiding excessive output to save computation) documents the transaction flow for later debugging. A production program might log only errors or state changes, keeping logs concise while still providing useful information.<\/p>\n
Reading blockchain data from Solscan’s logs also builds intuition about Solana’s execution model. A developer who has read hundreds of transaction logs understands the cost and timing of different operations, the patterns of successful versus failed transactions, and common mistakes. This knowledge transfers directly to writing more robust programs and catching bugs before deployment.<\/p>\n
Best practices for programs and developers reading logs<\/h2>\n
When writing a Solana program, log statements should be strategic. Logging every variable at every step consumes computation budget without providing much value after the program is debugged. Better practice is to log at decision points\u2014when the program makes a choice that affects the transaction outcome\u2014and when state changes. A program that logs “Starting transfer,” “Transfer verified,” and “Transfer complete” provides a trace without being verbose.<\/p>\n
Error messages should be specific. Instead of logging “Error occurred,” a program should log “Transfer failed: insufficient balance (required 1000, found 500).” The extra detail makes debugging far faster. Similarly, including relevant account addresses or amounts in logs makes it possible to correlate logs with on-chain data without having to reconstruct which account is which from the transaction structure.<\/p>\n
For developers reading logs, the first step is always to check the transaction status. A failed transaction requires different debugging than a succeeded one. If it failed, look at the instruction index where failure occurred and the error code. If the error code is a program-specific code, check the program’s documentation or source code for what that code means. If it is a runtime error like “out of compute,” examine the computation consumption logged at each instruction.<\/p>\n
When the error is ambiguous, compare against a successful transaction using the same program. The logs show the expected flow; deviations point to the problem. For account-related errors, verify the account addresses are correct and that the account meets the program’s requirements (ownership, signer status, data format). For authorization failures, confirm the transaction was signed by the required keys. For data errors, validate that frontend code constructs instruction data in the format the program expects.<\/p>\n
The role of logs in decentralized application auditing<\/h2>\n
When auditing a decentralized application, logs provide transparency into execution that code review alone cannot guarantee. A program might claim to perform a certain operation, but logs reveal whether it actually does. Security auditors and users both benefit from readable program logs. An auditor can trace complex multi-program interactions and confirm each step matches the specification. A user can verify their transaction executed as intended, even without reading the program code.<\/p>\n
However, logs are not a substitute for program audit or verification. A malicious program can lie in its logs or omit them entirely. Logs confirm what a program claims it did, but they cannot prove the program did the right thing. For truly critical operations, on-chain events (emitted data that becomes part of the permanent record and is harder to forge) provide stronger guarantees than logs. Nevertheless, for debugging, learning, and transparency, logs are essential.<\/p>\n
Solscan’s role as the official Solana blockchain explorer ensures that logs are displayed consistently and accurately. The platform serves developers, traders, NFT collectors, and crypto enthusiasts by making execution data accessible. A developer diagnosing a failed contract interaction can search by signature on Solscan immediately, without deploying local tools or syncing a full node. This accessibility accelerates debugging and reduces the barrier to understanding Solana’s execution model.<\/p>\n
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Frequently asked questions<\/h2>\n\n
Where can I find program logs for a Solana transaction?<\/h3>\n
Search the transaction signature on Solscan. Once the transaction page loads, scroll to the logs section at the bottom. You can expand it to full-screen view and search for specific text or program addresses within the logs. The logs are displayed chronologically with timestamps and source program identifiers.<\/p>\n<\/p><\/div>\n
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What does “Error Code 1” or “Program failed to complete successfully” mean?<\/h3>\n
This generic error means the program explicitly returned an error status. The actual reason appears in a program-specific error code or error message in the logs immediately following this message. Look for additional log entries or data that describes the failure more specifically, such as insufficient funds, invalid accounts, or authorization failure.<\/p>\n<\/p><\/div>\n
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How can I debug a transaction that failed due to compute budget exceeded?<\/h3>\n
Check the logs for compute consumption reported at each instruction. Identify which instruction consumed the most computation. If one instruction is near the budget limit (typically 200,000 units), that is the bottleneck. Optimize that instruction or reduce the number of instructions in the transaction. You may need to break the operation into multiple transactions or simplify the program logic.<\/p>\n<\/p><\/div>\n<\/div>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
A developer deploys a smart contract to the Solana blockchain, and a user’s transaction fails with a vague error code. The transaction landed on-chain, the fee was paid, but the intended operation did not complete. Without access to detailed execution logs, debugging becomes guesswork. Solana’s architecture produces execution traces at every step—instruction parsing, program invocation, […]<\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_elementor_edit_mode":"","_elementor_template_type":"","_elementor_data":"","_elementor_page_settings":null},"categories":[1],"tags":[],"class_list":["post-21216","post","type-post","status-publish","format-standard","hentry","category-1"],"_links":{"self":[{"href":"https:\/\/hemantpatil.org\/index.php?rest_route=\/wp\/v2\/posts\/21216","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/hemantpatil.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hemantpatil.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hemantpatil.org\/index.php?rest_route=\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/hemantpatil.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=21216"}],"version-history":[{"count":1,"href":"https:\/\/hemantpatil.org\/index.php?rest_route=\/wp\/v2\/posts\/21216\/revisions"}],"predecessor-version":[{"id":21217,"href":"https:\/\/hemantpatil.org\/index.php?rest_route=\/wp\/v2\/posts\/21216\/revisions\/21217"}],"wp:attachment":[{"href":"https:\/\/hemantpatil.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=21216"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hemantpatil.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=21216"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hemantpatil.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=21216"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
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