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@elopio elopio released this Oct 21, 2018 · 1168 commits to master since this release

OpenZeppelin 2.0 is finally here!!!

The major feature in this release is that we are now commiting to a stable API. In the process of stabilizing we've also reviewed a lot of the existing API in order to ensure a more straightforward experience for users.


Stable API

So far OpenZeppelin's API has sometimes changed from release to release, in backwards-incompatible ways. This has enabled us to iterate on features and design ideas, but we're at a point now where we want to commit to having a stable API and delivering reliable updates.

You can expect the external and internal API of contracts to remain stable. We're only making an exception to this for the contracts in the drafts/ subdirectory; this is where ERCs in Draft status, as well as more experimental contracts will go, and might have breaking changes in minor versions. We'll be documenting exactly what stability guarantees we provide in the coming weeks.

Granular permissions

Features which require permissions have used the almighty Ownable so far. We are now moving towards a more granular system of roles, like the MinterRole. Just like Ownable, the creator of a contract is assigned all roles at first, but they can selectively give them out to other accounts.

Improved test suite

Although this is not visible to users, we have been improving the test suite, increasing coverage to 100%, and cleaning up all of our tests, which had diverged in style. This is part of a bigger effort towards making contributing easier and involving our amazing contributors more in the entire process of building OpenZeppelin.

A new audit

The awesome LevelK team audited our 2.0.0 Release Candidate and they found some severe issues and suggested many improvements. We fixed almost all the issues and notes they reported, leaving only a few minor details for 2.1.0. Check out the LevelK Audit - OpenZeppelin 2.0 project for all the details.

We want to thank @cwhinfrey, @pcowgill and @shanefontaine for their very detailed reviews, high quality standards, and human support during the closing phase of this release. This audit gave us a great confidence boost on the code that we are now publishing.

Tons of community love

Now hold your breath, because this release was only possible because of the contributions of many, many people from everywhere in the world, and we want to thank all of them:

@3sGgpQ8H, @Aniket-Engg, @barakman, @BrendanChou, @cardmaniac992, @dougiebuckets, @dwardu, @facuspagnuolo, @fulldecent, @glesaint, @Glisch, @jacobherrington, @jbogacz, @jdetychey, @JeanoLee, @k06a, @lamengao, @ldub, @leonardoalt, @Miraj98, @mswezey23, @pw94, @shishir99111, @sohkai, @sweatyc, @tinchoabbate, @tinchou, @urvalla, @viquezclaudio, @vyomshm, @yaronvel, @ZumZoom.

Also we would like to thank all the people who are constantly helping others in our Slack channel, the ones who have given us feedback about the release, and the ones helping us triage and discuss our GitHub issues. If you are reading this wanting to jump in and make your first free software contributions, but you are unsure of where and how, talk to us! We can help you getting started, and we could use the extra hands.

With <3 from the maintainers team of this release.
-- @shrugs, @nventuro, @frangio and @elopio


The changelog is pretty big. We are introducing new concepts and new designs, together with many renames and restructures. If you have problems, comments or suggestions, please join our Slack channel.


  • Ownable contracts have moved to role based access. (#1291, #1302, #1303)
  • ERC contracts have all been renamed to follow the same convention. The interfaces are called IERC##, and their implementations are ERC##. Check out, for example, IERC20 and ERC20. (#1252, #1288)
  • All state variables are now private, which means that derived contracts cannot access them directly, but have to use getters. This is to increase encapsulation, to be able to reason better about the code. (#1197, #1265, #1267, #1269, #1270, #1268, #1281)
  • Events have been changed to be consistently in the past tense except for those which are defined by an ERC. (#1181)
  • Separated ERC721 into the different optional interfaces, and introduced ERC721Full which implements all. (#1304)
  • Added ERC165Query to query support for ERC165 interfaces. (#1086)
  • Added an experimental contract for migration between ERC20 tokens. (#1054)
  • Added SafeMath.mod. (#915)
  • Added Math.average. (#1170)
  • Added ERC721Pausable. (#1154)
  • Changed SafeMath to use require instead of assert. (#1187, #1120, interesting discussion!)
  • Removed restriction on who can release funds in PullPayments, PaymentSplitter, PostDeliveryCrowdsale, RefundableCrowdsale. (#1275)
  • Optimized ReentrancyMutex gas usage. (#1155)
  • Made ERC721.exists internal. (#1193)
  • Changed preconditions on PaymentSplitter constructor arguments. (#1131)
  • Fixed ERC721.getApproved to be in compliance with spec. (#1256)
  • Simplified interface of IndividuallyCappedCrowdsale. (#1296)
  • Renamed ERC20.decreaseApproval to decreaseAllowance, and changed its semantics slightly to be more secure. (#1293)
  • Renamed MerkleProof.verifyProof to MerkleProof.verify. (#1294)
  • Renamed ECRecovery to ECDSA, and AddressUtils to Address. (#1253)
  • Moved ECDSA and MerkleProof to a cryptography/ subdirectory. (#1253)
  • Moved ReentrancyGuard, and Address to a utils/ subdirectory. (#1253)
  • Renamed proposals/ subdirectory to drafts/. (#1271)
  • Moved TokenVesting, SignatureBouncer to drafts/. (#1271)
  • Removed ERC20Basic, now there's only ERC20. (#1125)
  • Removed Math.min64 and Math.max64, left only the uint256 variants. (#1156)
  • Removed Mint and Burn events from ERC20Mintable and ERC20Burnable. (#1305)
  • Removed underscores from event arguments. (#1258)
  • Removed a few contracts that we thought were not generally secure enough: LimitBalance, HasNoEther, HasNoTokens, HasNoContracts, NoOwner, Destructible, TokenDestructible, CanReclaimToken. (#1253, #1254, #1306)
  • Removed extensions of Owable: Claimable, DelayedClaimable, Heritable. (#1274)
  • Renamed AutoIncrementing to Counter and moved it to drafts\. ((1307, #1332)
  • Added events to roles on construction and when renouncing. (#1329)
  • Separated ERC721Mintable into two contracts, one with metadata (token URI) and one without. (#1365)
  • Added an ERC20 internal _transfer function. (#1370)
  • Added an Arrays library. (#1375)
  • Improved the OwnershipTransfer event and removed OwnershipRenounced. (#1397)
  • Removed the BreakInvariantBounty contract because of a front-running issue. (#1424)
  • Improved encapsulation on ERC165 making the _supportedInterfaces map private. (#1379)
  • Renamed RefundsEscrow event to RefundsClosed. (#1418)
  • Moved Escrow and RefundsEscrow to contracts/payment/escrow/. (#1430)
  • Made private the TokenVesting functions _releasableAmount and _vestedAmount. (#1427)
  • Made internal the constructors of contracts that should only be used inherited from others. (#1433, #1439)
  • Renamed ERC165 function supportsInterfaces to _supportsAllInterfaces. (#1435)
  • Added the address to Paused and Unpaused events. (#1410)
  • Renamed SplitPayment to PaymentSplitter, and added the events PayeeAdded, PaymentReleased and PaymentReceived. (#1417)
  • Renamed the TokenVesting events to TokensReleased and TokenVestingRevoked. (#1431)
  • Improved the SafeERC20 allowance handling. (#1407)
  • Made getCurrentRate from IncreasingPriceCrowdsale return 0 when the crowdsale is not open. (#1442)
  • Made tokenURI from ERC721Metadata external, to match the specification. (#1444)
  • Fixed a reentrancy issue on FinalizableCrowdsale. (#1447)
  • Fixed how allowance crowdsale checks remaining tokens. (#1449)
  • Added the nonReentrant safeguard for buyTokens in the Crowdsale contract. (#1438)
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