View source for Solidity

{{Short description|Programming language}}
{{About|the programming language|the state of matter|Solid}}
{{primary sources|date=May 2021}}
{{Use dmy dates|date=July 2018}}
{{Infobox programming language
| name = Solidity
| logo = Solidity logo.svg
| logo caption = The Solidity language logo
| logo size = 80px
| paradigm = [[Imperative_programming|Imperative]]
| file ext = .sol
| released = August 2014
| designer = [[Gavin Wood]]
| developer = Christian Reitwiessner,<ref>{{Cite web |title=Contributors to ethereum/solidity |url=https://github.com/ethereum/solidity |access-date=2023-03-30 |website=GitHub |language=en}}</ref> Alex Beregszaszi,<ref>{{Cite web |title=Contributors to ethereum/solidity |url=https://github.com/ethereum/solidity |access-date=2023-03-30 |website=GitHub |language=en}}</ref> and several former [[Ethereum]] core contributors.
| programming language = [[C%2B%2B|C++]]<ref>{{Cite web |title=Build software better, together |url=https://github.com/ |access-date=2023-03-30 |website=GitHub |language=en}}</ref>
| latest release version = {{wikidata|property|reference|P348}}
| latest release date    = {{start date and age|{{wikidata|qualifier|P348|P577}}}}
| influenced_by = [[JavaScript]], [[C++]], [[Python (programming language)|Python]]
| license = [[GNU General Public License#Version 3|GNU General Public License v3.0]]<ref>{{Citation |title=The Solidity Contract-Oriented Programming Language |date=2023-03-30 |url=https://github.com/ethereum/solidity/blob/bca3fb8ffd7c57a3f6920fd5a115a9a0fc0edb21/LICENSE.txt |access-date=2023-03-30 |publisher=ethereum}}</ref>
| website = {{URL|https://soliditylang.org}}
}}

'''Solidity''' is a [[programming language]] for implementing [[smart contract]]s<ref>{{Cite web|url=https://www.huffpost.com/entry/ethereum-is-the-second-most-valuable-digital-currency_b_596bc5c7e4b022bb9372b2b2|title=Ethereum Is The Second Most Valuable Digital Currency, Behind Bitcoin|last1=Afshar|first1=Vala|date=2017-07-17|website=HuffPost|language=en|access-date=2019-04-10}}</ref><ref name="finextra24Nov2016">{{cite news |date=24 November 2016 |url=https://www.finextra.com/newsarticle/29813/sofe-berlin-swift-unveils-blockchain-proof-of-concept |title=SOFE Berlin: Swift unveils blockchain proof-of-concept |work=Finextra |type=News|access-date=24 November 2016}}</ref> on various [[blockchain]] platforms, most notably, [[Ethereum]].<ref>{{cite magazine |title=Someone Just Stole $50 Million from the Biggest Crowdfunded Project Ever. (Humans Can't Be Trusted) |url=https://www.wired.com/2016/06/50-million-hack-just-showed-dao-human/ |magazine=Wired |language=en-us|last1=Finley |first1=Klint }}</ref> Solidity is licensed under [[GNU General Public License#Version 3|GNU General Public License v3.0]].<ref>{{Citation |title=The Solidity Contract-Oriented Programming Language |date=2023-03-30 |url=https://github.com/ethereum/solidity/blob/bca3fb8ffd7c57a3f6920fd5a115a9a0fc0edb21/LICENSE.txt |access-date=2023-03-30 |publisher=ethereum}}</ref> Solidity was designed by [[Gavin Wood]]<ref>{{Cite web |last=Wood |first=Gavin |date=January 13, 2015 |title=Created Solidity |url=https://github.com/ethereum/wiki/commit/a7849d4089240c00dc1974b469fe5053852df687?short_path=78b9c36#diff-78b9c36766ad236b6a23f87a983e91c2d18634e32bcd5f8d2d8e34322c7ecfb1 |access-date=2024-03-23 |website=Ethereum Wiki (Archived)}}</ref>{{primary source inline|date=February 2024}} and developed by Christian Reitwiessner, Alex Beregszaszi, and several former Ethereum core contributors.<ref>{{cite web|url=https://github.com/ethereum/solidity/graphs/contributors|title=List of contributors|website=[[GitHub]]}}</ref> Programs in Solidity run on [[Ethereum#Virtual machine|Ethereum Virtual Machine]] or on compatible virtual machines.<ref>{{Cite book |last=College |first=A. M. C. |url=https://books.google.com/books?id=l96YEAAAQBAJ&dq=%22Solidity%22+-wikipedia&pg=PA20 |title=Blockchain & Cryptocurrency Technology with Solidity Level 1 |date=2022-11-01 |publisher=Advanced Micro Systems Sdn Bhd |language=en}}</ref>

==History==
Solidity was proposed in August 2014 by [[Gavin Wood]]<ref>{{Cite web |title=Gavin Wood |url=https://gavwood.com/ |url-status=dead |archive-url=https://web.archive.org/web/20230330221513/https://gavwood.com/ |archive-date=30 March 2023 |access-date=2023-03-30 |website=gavwood.com}}</ref>{{primary source inline|date=February 2024}} The language was later developed by the [[Ethereum]] project's Solidity team, led by Christian Reitwiessner.

Solidity is the primary language used to develop [[Smart contract|smart contracts]] for [[Ethereum]] as well as other private [[Blockchain|blockchains]], such as the enterprise-oriented [[Hyperledger]] Fabric blockchain. [[SWIFT]] deployed a proof of concept using Solidity running on Hyperledger Fabric.<ref>{{cite arXiv |eprint=1802.06038 |class=cs.CR |first1=Ivica |last1=Nikolic |first2=Aashish |last2=Kolluri |title=Finding The Greedy, Prodigal, and Suicidal Contracts at Scale |date=14 March 2018 |last3=Sergey |first3=Ilya |last4=Saxena |first4=Prateek |last5=Hobor |first5=Aquinas |quote=Different source languages compile to the EVM semantics, the predominant of them being Solidity}}</ref><ref>{{Cite web |title=Westpac joins SWIFT's blockchain proof of concept |url=https://www.zdnet.com/article/westpac-joins-swifts-blockchain-proof-of-concept/ |access-date=2022-07-13 |website=ZDNet |language=en}}</ref>

== Description ==
Solidity is a [[statically typed programming language]] designed for developing [[Smart contract|smart contracts]] that run on the [[Ethereum#Virtual machine|Ethereum Virtual Machine]] (EVM) or compatible virtual machines.<ref>{{Cite web|url=https://developer.ibm.com/patterns/loyalty-points-fabric-evm/|title=Hyperledger Fabric Tutorial - Create a blockchain app for loyalty points|website=IBM Developer|language=en-US|access-date=2019-04-10}}</ref>

Solidity uses [[ECMAScript]]-like syntax which makes it familiar for existing web developers;<ref>{{Cite web |title=Language Influences — Solidity 0.8.17 documentation |url=https://docs.soliditylang.org/en/v0.8.17/language-influences.html |access-date=2023-03-30 |website=docs.soliditylang.org}}</ref> however unlike ECMAScript it has [[Type system#Static type checking|static typing]] and [[variadic]] return types. Solidity is different from other EVM-targeting languages such as [[Ethereum#Programming_languages|Serpent]] and [[Ethereum#Programming_languages|Mutan]] in some important ways. It supports complex [[Member variable|member variables]] for [[Smart contract|smart contracts]], including arbitrarily hierarchical mappings and [[record (computer science)|structs]]. Solidity [[smart contract]] support [[inheritance (object-oriented programming)|inheritance]], including [[multiple inheritance]] with C3 linearization. Solidity introduces an [[application binary interface]] (ABI) that facilitates multiple [[type-safe]] functions within a single [[smart contract]] (this was also later supported by Serpent). The Solidity proposal also includes "Natural Language Specification", a documentation system for specifying user-centric descriptions of the ramifications of [[Method (computer programming)|method]]-calls.{{Sfn|Kapetanios-2008-06-27|p=309}}<ref>{{cite web|url=https://github.com/ethereum/wiki/wiki/Ethereum-Natural-Specification-Format|title=Ethereum Natural Specification Format|author=ethereum|work=GitHub}}</ref>{{Primary source inline|date=December 2018}}

Example of a Solidity program:<ref>{{Cite web |title=Introduction to Smart Contracts — Solidity 0.8.19 documentation |url=https://docs.soliditylang.org/en/v0.8.19/introduction-to-smart-contracts.html#subcurrency-example |access-date=2023-03-30 |website=docs.soliditylang.org}}</ref>{{r|Bhargavan-2016-08-27}}
<syntaxhighlight lang="solidity">
// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.4;

contract Coin {
    // The keyword "public" makes variables
    // accessible from other contracts
    address public minter;
    mapping(address => uint) public balances;

    // Events allow clients to react to specific
    // contract changes you declare
    event Sent(address from, address to, uint amount);

    // Constructor code is only run when the contract
    // is created
    constructor() {
        minter = msg.sender;
    }

    // Sends an amount of newly created coins to an address
    // Can only be called by the contract creator
    function mint(address receiver, uint amount) public {
        require(msg.sender == minter);
        balances[receiver] += amount;
    }

    // Errors allow you to provide information about
    // why an operation failed. They are returned
    // to the caller of the function.
    error InsufficientBalance(uint requested, uint available);

    // Sends an amount of existing coins
    // from any caller to an address
    function send(address receiver, uint amount) public {
        if (amount > balances[msg.sender])
            revert InsufficientBalance({
                requested: amount,
                available: balances[msg.sender]
            });

        balances[msg.sender] -= amount;
        balances[receiver] += amount;
        emit Sent(msg.sender, receiver, amount);
    }
}
</syntaxhighlight>

==Development IDEs==
* [[Visual Studio Code | Microsoft Visual Studio Code]]
* [[IntelliJ IDEA | JetBrains IntelliJ]]
* [[Remix Online Editor]]<ref>{{Cite web |title=Remix - Ethereum IDE |url=https://remix.ethereum.org/ |access-date=2023-03-30 |website=remix.ethereum.org}}</ref>

==Editor extensions==
* Solidity Support for Visual Studio Code<ref>{{Cite web |title=solidity - Visual Studio Marketplace |url=https://marketplace.visualstudio.com/items?itemName=JuanBlanco.solidity |access-date=2023-03-30 |website=marketplace.visualstudio.com |language=en-us}}</ref>
* Solidity Support For IntelliJ<ref>{{Cite web |title=Solidity - IntelliJ IDEs Plugin {{!}} Marketplace |url=https://plugins.jetbrains.com/plugin/9475-solidity |access-date=2023-03-30 |website=JetBrains Marketplace}}</ref>
* Aderyn<ref>{{Cite web |title=Aderyn - Visual Studio Marketplace |url=https://marketplace.visualstudio.com/items?itemName=Cyfrin.aderyn |access-date=2025-06-09 |website=marketplace.visualstudio.com |language=en-us}}</ref>

==Blockchain platforms==
Solidity is available on:
* [[Avalanche_(blockchain_platform)|Avalanche C-Chain]]
* [[Binance Smart Chain]]<ref>{{Cite web|title=Binance Smart Chain|website=[[GitHub]]|date=26 October 2021|url=https://github.com/binance-chain/bsc}}</ref>
* [[Counterparty (technology)|Counterparty]] (which runs on [[Bitcoin]])<ref>{{Cite news|last=Vigna|first=Michael J. Casey and Paul|date=2014-11-12|title=BitBeat: Bitcoin 2.0 Firm Counterparty Adopts Ethereum's Software|language=en-US|work=Wall Street Journal|url=https://blogs.wsj.com/moneybeat/2014/11/12/bitbeat-bitcoin-2-0-firm-counterparty-adopts-ethereums-software/|access-date=2021-04-16|issn=0099-9660}}</ref><ref>{{Cite book|last=Swan|first=Melanie|url=https://www.worldcat.org/oclc/900781291|title=Blockchain : blueprint for a new economy|date=2015|isbn=978-1-4919-2047-3|edition=1st.|location=[Sebastopol, Calif.]|oclc=900781291}}</ref>
* [[Ethereum]]
* [[Ethereum Classic]]
* [[TRON (cryptocurrency)|Tron]]
* [[Hashgraph|Hedera Hashgraph]]
* Polygon
* [[Metis (blockchain layer 2)|Metis]]
* Arbitrum
* Optimism
* [https://www.zksync.io/ ZKsync Era]

==Criticism==
Many security properties of smart contracts are inherently difficult to reason about directly, and the [[Turing-completeness]] of Solidity means that verification of arbitrary properties cannot be [[undecidable problem|decidably]] automated. Current automated solutions for smart contract security analysis can miss critical violations, produce false positives, and fail to achieve sufficient code coverage on realistic contracts.<ref>{{cite book |last1=Tsankov |first1=Petar |last2=Dan |first2=Andrei |last3=Drachsler-Cohen |first3=Dana |last4=Gervais |first4=Arthur |last5=Bünzli |first5=Florian |last6=Vechev |first6=Martin |chapter=Securify: Practical Security Analysis of Smart Contracts |title=Proceedings of the 2018 ACM SIGSAC Conference on Computer and Communications Security |publisher=Association for Computing Machinery |pages=67–82 |doi=10.1145/3243734.3243780 |date=15 October 2018|arxiv=1806.01143 |hdl=10044/1/87935 |isbn=978-1-4503-5693-0 |s2cid=46936025 }}</ref> Solidity has been blamed for the error-prone implementation of Ethereum smart contracts due to its counterintuitive nature, its lack of constructs to deal with blockchain domain-specific aspects, and its lack of centralized documentation of known vulnerabilities.<ref>{{cite book |last1=Atzei |first1=Nicola |last2=Bartoletti |first2=M. |last3=Cimoli |first3=Tiziana |title=Principles of Security and Trust, 6th International Conference, 2017, Proceedings |chapter=A Survey of Attacks on Ethereum Smart Contracts (SoK) |series=Lecture Notes in Computer Science |date=2017 |pages=164–186 |doi=10.1007/978-3-662-54455-6_8 |isbn=978-3-662-54454-9 |s2cid=15494854 }}</ref>

In 2016, a [[Cornell University]] researcher stated that Solidity was partially to blame for [[The DAO (organization)|The DAO]] hack that took place that year. He stated: "this was actually not a flaw or exploit in the DAO contract itself: technically the [[Ethereum#Virtual machine|Ethereum Virtual Machine]] (EVM) was operating as intended, but Solidity was introducing security flaws into contracts that were not only missed by the community, but missed by the designers of the language themselves."<ref name="wiredjune18th2016">{{cite magazine |first1=Klint |last1=Finley |date=18 June 2016 |url=https://www.wired.com/2016/06/50-million-hack-just-showed-dao-human/ |title=A $50 Million Hack Just Showed That the DAO Was All Too Human |magazine=Wired |type=News |access-date=18 February 2017}}</ref>

The developers community often cites Solidity requiring much of third party interfaces and APIs, and its inability to create critical information intensive smart contracts.

== Comparison with other smart contract languages ==

=== Solidity vs. Rust ===
Solidity is the primary programming language for developing smart contracts on the Ethereum Virtual Machine (EVM).<ref>{{Cite book |last1=Zheng |first1=Gavin |url=https://books.google.com/books?id=OGn6DwAAQBAJ&dq=%22Solidity%22+-wikipedia&pg=PR7 |title=Ethereum Smart Contract Development in Solidity |last2=Gao |first2=Longxiang |last3=Huang |first3=Liqun |last4=Guan |first4=Jian |date=2020-08-31 |publisher=Springer Nature |isbn=978-981-15-6218-1 |language=en}}</ref> However, [[Rust (programming language)|Rust]] has emerged as a strong alternative in the blockchain ecosystem, especially for blockchains that support [[WebAssembly]] (Wasm), such as [[Polkadot (blockchain platform)|Polkadot]], [[Klever blockchain|Klever]] and [[Solana (blockchain platform)|Solana]].

==== Memory safety ====
Rust offers built-in [[memory safety]] features that prevent common programming errors, such as [[null pointer]] dereferencing and [[buffer overflow]]s, which are not as rigorously enforced in Solidity. This makes Rust contracts potentially less prone to security vulnerabilities that could be exploited in smart contract environments.

==== Concurrency ====
Rust supports concurrent programming, which allows developers to write highly performant code that can handle multiple tasks simultaneously. This is particularly beneficial for high-performance blockchains like Solana,<ref>{{Cite web |title=Developing with Rust {{!}} Solana |url=https://solana.com/docs/programs/lang-rust |access-date=2024-08-16 |website=solana.com |language=en}}</ref> which need to process thousands of transactions per second. Solidity, on the other hand, does not natively support concurrency, which can limit its performance in certain applications.<ref>{{Cite web |title=Rust Official Documentation |url=https://www.rust-lang.org/}}</ref>

==== Ecosystem integration ====
While Solidity is deeply integrated with the Ethereum ecosystem and its numerous development tools,<ref>{{Cite web |title=Solidity Lang |url=https://soliditylang.org/}}</ref> Rust is versatile and can be used across various blockchain platforms that leverage Wasm. Rust’s growing popularity is reflected in its adoption by new blockchain projects that prioritize performance and security.

==== Domain Specific Language ====
One of the major benefits of Solidity over other languages, is that it was designed specifically for smart contracts as a [[Domain-specific language|domain specific language]]. This enables developers to build code with built-in smart contract capabilities like [https://www.cyfrin.io/glossary/gas gas] and [https://www.cyfrin.io/glossary/storage-solidity storage] without having to have the language abstract the concepts out.

==References==
{{Reflist|refs=
<ref name        = Bhargavan-2016-08-27>
{{cite journal
 | url           = http://research.microsoft.com/en-us/um/people/nswamy/papers/solidether.pdf
 | last1         = Schneier
 | first1        = Karthikeyan
 | last2         = Schneier
 | first2        = Antoine
 | last3         = Bhargavan
 | first3        = Cedric
 | last4         = Delignat-Lavaud
 | first4        = Anitha
 | last5         = Fournet
 | first5        = Gollamudi
 | last6         = Schneier
 | first6        = Bruce
 | last7         = Rastogi
 | first7        = Nadim
 | last8         = Sibut-Pinote
 | first8        = Aseem
 | last9         = Rastogi1
 | first9        = Thomas
 | last10        = Swamy
 | first10       = Nikhil
 | last11        = Zanella-Beguelin
 | first11       = Santiago
 | date          = 27 August 2016
 | title         = Short Paper: Formal Verification of Smart Contracts
 | journal       = Microsoft Research, French Institute for Research in Computer Science and Automation, Harvard University
 | language      = en
 | archive-url   = https://web.archive.org/web/20160827092146/http://research.microsoft.com/en-us/um/people/nswamy/papers/solidether.pdf
 | url-status    = live
 | archive-date  = 27 August 2016
}}</ref>
}}

{{Cryptocurrencies}}

[[Category:Domain-specific programming languages]]
[[Category:Statically typed programming languages]]
[[Category:Ethereum]]