How have BTC and Bitcoin Cash diverged through upgrades?

Bitcoin (BTC) and Bitcoin Cash (BCH) have diverged in many ways through upgrades on each chain, particularly through the numerous upgrades on Bitcoin Cash. The following categories illustrate many of the key divergences.

• BTC: Maintained its 1 MB block size limit, relying on Segregated Witness (SegWit) and off-chain solutions like the Lightning Network for scalability. Results in a constantly congested network.
• Bitcoin Cash: Eliminated the hard block size limit and introduced a configurable block size. It successfully increased the Excessive Blocksize limit (EB) to 32 MB, aiming for higher throughput. A May 2024 upgrade will will activate an adaptive block size limit algorithm that will constantly adjust the block size, with a baseline of 32 MB, as the needs of the network evolve.

• BTC: Retained its opt-in Replace-By-Fee (RBF) policy and is poised to introduce full RBF by default.
• Bitcoin Cash: Removed RBF, emphasizing swift and hassle-free transactions in everyday commerce.

• BTC: Continued to use legacy addresses.
• Bitcoin Cash: Introduced CashAddr format for clarity and to prevent confusion with BTC addresses.

• BTC: No significant introduction or reintroduction of opcodes.
• Bitcoin Cash: Reintroduced old opcodes and added new opcodes, providing flexibility for data manipulation, native introspection, and diverse applications.

• BTC: No change in OP_RETURN size.
• Bitcoin Cash: Increased OP_RETURN size to 220 bytes, enabling more data storage for various applications. Enabled multiple OP_RETURNs.

• BTC: No standardized transaction ordering protocol.
• Bitcoin Cash: Implemented Canonical Transaction Ordering (CTOR) for consistent block reconstruction and improved block propagation.

• BTC: No specific protocol introduced.
• Bitcoin Cash: Implemented Graphene for faster block propagation. More advanced protocols like XThinner and BlockTorrent in development.

• BTC: No specific opcodes for external message validation.
• Bitcoin Cash: Introduced OP_CHECKDATASIG and OP_CHECKDATASIGVERIFY for validating messages from external oracles.

• BTC: Implemented Schnorr signatures via the Taproot soft fork upgrade.
• Bitcoin Cash: Adopted Schnorr signatures natively for enhanced privacy, scalability, and non-malleability.

• BTC: Retained a limit on unconfirmed transaction chains.
• Bitcoin Cash: Eliminated the limit, allowing flexibility in scenarios involving frequent transactions.

• BTC: Continued with the original difficulty adjustment algorithm.
• Bitcoin Cash: Transitioned through various algorithms, including CW-144 and ASERT, for improved stability and block time targeting.

• BTC: No network-wide standard for detecting double-spends.
• Bitcoin Cash: Introduced Double-Spend Proofs to provide merchants rapid notifications of attempted fraud.

• BTC: No notable improvements to the virtual machine.
• Bitcoin Cash: Introduced bigger script integers and Pay-To-Script-Hash-32, allowing for more powerful and secure options.

• BTC: No direct support for native tokens.
• Bitcoin Cash: Implemented CashTokens, enabling native tokens on the blockchain with the power of BCH scripting capabilities, allowing for many new and diverse use cases.

• BTC: No specific protocols or plans for faster syncing.
• Bitcoin Cash: In development, allowing for faster and trustless syncing.

• BTC: No specific plans for reusable payment addresses.
• Bitcoin Cash: In development, aiming to simplify recurring payments while maintaining privacy.

BTC has generally opted for conservative upgrades, off-chain scaling solutions, and maintaining a smaller block size. In contrast, Bitcoin Cash's approach has been marked by frequent hard forks, rapid development, and a focus on on-chain scalability and usability. Both have evolved in response to their respective visions and community priorities.

Learn more in our deep dive into the differences between BTC and Bitcoin Cash.