Bitcoin Core 30.0 released with new features, bug fixes, and performance improvements

Bitcoin Core 30.0 is poised to be one of the most consequential upgrades in the client’s history. With enhancements ranging from higher signature limits to improved OP_RETURN support, lower default fees, and major wallet/GUI changes, this release aims to refine how full nodes, wallets, and users interact with Bitcoin. If you’re running version 27.x or older, now is the time to consider upgrading. In this post, we’ll dive deep into the new features, bug fixes, performance improvements, migration advice, and possible caveats you should watch out for.

What’s The Point Of this

Before we get into specifics, it’s helpful to understand why version 30.0 is drawing so much attention. Bitcoin Core has historically followed a cadence of major releases every 6–7 months, with maintenance releases in between. (Bitcoin Core) Version 30.0 is shaping up to be a “big milestone” release with changes that are less incremental and more transformational.

In particular, two areas stand out:

1. Data handling / transaction policy — especially lifting or expanding limits on OP_RETURN data
2. Wallet / GUI architecture — in particular, removing legacy wallets and migrating to Qt6

Together, these changes have implications not only technically, but philosophically — they raise questions about how Bitcoin should evolve. But from a user’s perspective, there are many concrete benefits, which we cover next.

What’s New: Major Feature Enhancements

Here are the headline improvements in Bitcoin Core 30.0:

1. Higher Signature Operation Limits

One of the technical bottlenecks in Bitcoin’s validation logic involves signature operation limits (sigops). When a transaction or script contains many signature checks, nodes enforce caps to prevent denial-of-service (DoS) style attacks or resource exhaustion. Version 30.0 raises these limits, which allows more complex scripting or contract-like functionality in transactions without hitting the ceiling prematurely.

By increasing the allowed sigops in policy and consensus layers, developers hope to enable more sophisticated on-chain protocols (e.g. multi-sig schemes, express validation logic) without being throttled. In effect, this gives more breathing room to advanced transaction types while still guarding the network against abuse.

2. Better OP_RETURN Output Support

Perhaps the most discussed change in 30.0 is how it handles OP_RETURN outputs. Historically, Bitcoin limited OP_RETURN payloads to 80 bytes per output, as a way to allow minimal data storage but prevent blockchain bloat. (Decrypt)

In the new release, that 80-byte limit is essentially removed: each OP_RETURN output may now carry up to 4 MB of arbitrary data, by default. (Decrypt)

This policy shift is huge. It allows, for example, embedding full documents, images, or metadata directly on-chain (within the block and consensus limits). That said, the number of OP_RETURN outputs and total size are still bounded by block size / weight rules, sigop limits, and mempool policy. (Cryptopolitan)

Critics warn that this change may encourage “blockchain as storage” rather than minimal transactional logic. (Cointelegraph) Supporters counter that the fee market will naturally deter spam and that modern use cases (e.g. inscriptions, decentralized identifier anchoring) benefit from this flexibility. (Decrypt)

3. Lower Default Fees

To make ordinary transactions more efficient, Bitcoin Core 30.0 also lowers the default fee rate (fee per unit of virtual size). While the precise numbers may depend on mempool conditions and fee estimation logic, the goal is clear: default transactions become cheaper for users, especially in less-congested periods.

Lowering default fees must be done carefully, because if set too low, transactions might stall or be repriced upward by fee bumping logic. But coupled with more flexible scripting limits and improved mempool management, 30.0 aims to balance safety, usability, and cost.

Wallet & GUI Changes: A New Era

Beyond protocol-level improvements, Bitcoin Core 30.0 contains major changes in how wallets are structured, and how the GUI is built and maintained.

Legacy Wallet Removal & Migration Strategy

One of the boldest steps is removing legacy wallet support. Over time, Bitcoin Core has supported “legacy” wallets (based on BerkeleyDB and older formats) alongside more modern “descriptor” wallets. (GitHub) In version 30.0, the deprecated legacy wallets and associated formats are slated for removal.

What that means:

• You cannot create new legacy wallets in 30.0
• If you currently use a legacy wallet (especially from version 27.x or earlier), you’ll need to migrate it to a descriptor wallet
• The built-in migratewallet command (introduced earlier) will be essential
• Users who delay upgrading may find their old .dat wallets unsupported or harder to restore

Note: some users attempting to recover very old wallet dat files have already noted deprecation warnings: “The legacy wallet type is being deprecated… support will be removed in future releases.” (Bitcoin Stack Exchange) Always back up your wallet, export private keys if necessary, and test the migration in a safe environment.

The timeline for this transition has been in the works for years. The proposal to remove legacy wallets and BDB support was first discussed around 2020. (GitHub) Version 26.0 already disallowed creating new legacy wallets. (Bitcoin Core) Hence 30.0 is where the final cut occurs.

Qt 6 Migration & GUI Overhaul

Another major change is the GUI’s migration from Qt5 to Qt6. The Bitcoin-Qt (desktop wallet) and GUI front-end will be rebuilt on a newer framework, which should yield better performance, more modern styling, greater maintainability, and improved cross-platform support.

Combined with the removal of legacy wallet UIs, the GUI code base becomes leaner and more modern. This can lead to faster builds, fewer bugs, and a more consistent user experience. However, it also means more careful testing is required, especially for users relying on particular GUI features or custom plugins.

Bug Fixes & Performance Improvements

Of course, version 30.0 is not all about flags and limits — it also contains many under-the-hood fixes and optimizations. While the complete release notes are available in the devwiki and GitHub repo, here are some standout improvements and general trends:

• Mempool and relay improvements: better filtering, ancestor/descendant checks, and policy tweaks help reduce spam and improve transaction relaying under load
• Block and UTXO database optimizations: more efficient caching, indexing, and selective flushing reduce I/O overhead in busy nodes
• Validation speed-ups: by rearranging some common-case logic and caching reused results, overall block validation is marginally faster
• Crash / corner-case fixes: situations (especially during startup, upgrade, or extreme chain reorganizations) that previously led to failures have been hardened
• RPC & CLI refinements: deprecated or redundant RPCs were cleaned up; some commands now behave more predictably under edge conditions
• Backward compatibility patches: for nodes upgrading from older versions (e.g. 27.x, 28.x), extra migration logic ensures smooth transitions for most users

Because Bitcoin Core is open source, you can review the full list of merged pull requests, issue trackers, and release candidate notes on GitHub (for example, issue tracker 32275 for release schedule) (GitHub) or devwiki pages for 30.0.

Upgrade Path & Compatibility Advice

If you are running version 27.x or older, it’s strongly advisable to plan your upgrade to 30.0 safely. Here are recommended steps:

1. Backup everything — wallet files, config, data directory
2. Test migration — on a copy of your node, run migratewallet (or equivalent) to convert legacy wallets to descriptor form
3. Install version 29 or 28 as intermediate if you’re in a very old version, to smooth out compatibility issues
4. Upgrade to 30.0 RC (release candidate) first, then to the stable release when ready
5. Verify node syncing, GUI behavior, RPCs post-upgrade before trusting large transactions

Nodes that stay too far behind risk being unable to parse or validate new blocks (if consensus changes), or not benefiting from critical performance fixes.

Also note that the migration away from legacy wallets is irreversible in future versions — after 30.0, legacy formats may be entirely unsupported.

Potential Risks & Community Debate

Because Bitcoin is an ecosystem built on both code and philosophy, changes like those in 30.0 inevitably generate controversy. Some of the key debates include:

• Blockchain bloat: Critics argue that loosening OP_RETURN limits effectively allows the blockchain to be used as a data storage layer, leading to permanent bloat and higher costs for node operators. (Cointelegraph)
• Legal risk for nodes: Some worry that node operators could be exposed legally if illicit data is encoded into the chain via large OP_RETURN payloads. (Cointelegraph)
• Centralization pressure: If the cost of storage or verification grows, some argue only well-resourced nodes might continue running, reducing decentralization
• Fee market distortions: Lower default fees or more script complexity might create tensions in fee estimation or mempool behavior under congestion
• Backward-breaking changes: As always, migrating legacy wallet users or GUI users may discover bugs or regressions not foreseen in testing

Still, supporters contend that Bitcoin must evolve, and that the fee market and consensus rules will limit misuse. The fact that the removal of the OP_RETURN limit was approved after significant developer debate suggests the change was not taken lightly. (CoinDesk) As one article put it, “Bitcoin Core 30 lets users store megabytes, not just bytes.” (BitDegree)

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Summary & CTA

In summary:

• Bitcoin Core 30.0 is a transformative upgrade, bringing higher signature limits, expanded OP_RETURN support, lower default fees, and wallet/GUI rewrites
• Legacy wallet removal and Qt6 migration are central to the release’s user-facing changes
• Performance improvements and bug fixes round out the upgrade
• Users on version 27.x or older should not delay upgrading
• Thoughtful migration and backups are crucial
• The release is controversial, particularly around data storage vs. minimalism

Internal & External Links

• For more on how to migrate wallets, see our guide: Migrate Legacy to Descriptor Wallets (internal)
• For background on Bitcoin Core’s version history and official releases, refer to the Bitcoin Core Releases Page (Bitcoin Core)
• For the GitHub release schedule and development tracker, see Issue #32275 on GitHub (GitHub)
• To read deeper technical and community perspectives, see this Coindesk article on OP_RETURN changes (CoinDesk)
• For coverage of the OP_RETURN debate, check Decrypt’s write-up on data storage changes in Core 30.0 (Decrypt)

Final Thoughts

Bitcoin Core 30.0 isn’t just “another update” — it reflects a philosophical and functional pivot in how the reference client approaches data, wallets, and usability. While its success hinges on careful transitions and community buy-in, it’s undeniable that many of the changes push Bitcoin’s software stack forward.

If you’re managing a full node, using Core’s GUI wallet, or developing integrations, be proactive: plan your migration path, back up your data, test with release candidates, and keep abreast of community feedback. In doing so, you’ll help ensure your setup is ready for the future — not just maintaining the past.

Let me know if you want me to produce a condensed social-media summary, or a version optimized for mobile readers.

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References / Sources

1. “Bitcoin Core 30 to Increase OP_RETURN Data Limit After Developer Debate Concludes,” Coindesk. (CoinDesk)
2. “Bitcoin Core v30.0 release candidate is available,” Delving Bitcoin / devwiki. (Delving Bitcoin)
3. “Bitcoin Core Devs Commit to Changing OP_RETURN Data Storage Limit,” Decrypt. (Decrypt)
4. “Bitcoin Core Version 30: OP_RETURN Expansion Debate,” BeinCrypto. (BeInCrypto)
5. “Bitcoin Core 30 lets users store megabytes, not just bytes,” Bitdegree. (BitDegree)
6. “Proposed Timeline for Legacy Wallet and BDB removal,” GitHub Issue #20160. (GitHub)
7. “Bitcoin Core 26.0,” Bitcoin Core official release notes. (Bitcoin Core)
8. “Release Schedule for 30.0,” GitHub Issue #32275. (GitHub)
9. “Recover my old wallet,” Bitcoin StackExchange. (Bitcoin Stack Exchange)
10. “Bitcoin Core Version History,” Bitcoin.org. (Bitcoin)
11. “Bitcoin Core 30 Update to Raise Limit on Controversial OP_RETURN,” UnchainedCrypto. (Unchained)
12. “Bitcoin Core to revise some parameters in the next major update,” Cryptopolitan. (Cryptopolitan)
13. “Bitcoin Core v30 Sparks Debate Over OP_RETURN Cap Removal,” AInvest. (AInvest)
14. Wikipedia, “Bitcoin Core.” (en.wikipedia.org)