SegWit được hé lộ: Nâng cấp mở rộng quy mô quan trọng của Bitcoin ảnh hưởng thế nào đến giao dịch của bạn

Network congestion and high transaction fees on the Bitcoin network have long been a pain point for both users and developers. In August 2017, a protocol upgrade known as Segregated Witness (SegWit) was activated via a soft fork, quietly transforming the landscape.

This was more than a technical adjustment—it marked a pivotal decision shaping Bitcoin’s future direction.

01 The Core of SegWit Technology

SegWit, short for "Segregated Witness," introduced a fundamental innovation by reorganizing the structure of transaction data. Before this upgrade, signature data used to unlock Bitcoin was intertwined with the main transaction information.

This design led to two major issues: transaction malleability and block size limitations.

After SegWit was implemented, signature data was separated from the main transaction and moved into a new field called "witness data." This seemingly simple change had far-reaching consequences: transaction IDs no longer included signature information, which fundamentally eliminated the possibility for third parties to alter transaction IDs before confirmation.

02 Solving Transaction Malleability

Transaction malleability once posed a serious threat to the Bitcoin ecosystem. This vulnerability allowed attackers to tweak signature data after a transaction was broadcast but before it was confirmed, thereby changing the transaction ID without invalidating the transaction itself.

This flaw was exploited in double-spending attacks and even indirectly contributed to the collapse of the Mt.Gox exchange.

By removing signature data from the transaction ID calculation, SegWit completely resolved this issue. Now, transaction IDs are derived solely from the core transaction data, making them immutable once generated.

This improvement not only strengthened the security of the Bitcoin network but also cleared technical hurdles for building more complex second-layer protocols, such as the Lightning Network.

03 Real-World Impact on Block Capacity

SegWit cleverly achieved effective block size expansion by introducing a new metric called "block weight." Traditionally, block size was capped at 1,000,000 bytes (1 MB). SegWit, however, set the block weight limit at 4,000,000 weight units.

Under this new system, each byte of regular transaction data counts as 4 weight units, while each byte of witness data counts as only 1 weight unit.

This differentiated accounting means that witness data takes up about 75% less space in a block, freeing up room for more transactions. Based on typical transaction compositions, SegWit effectively increased Bitcoin’s block capacity from 1 MB to approximately 1.8 MB, significantly boosting network throughput.

04 Evolution of Address Types

With the rollout of SegWit, Bitcoin address formats also evolved. There are now three main types of Bitcoin addresses:

Legacy addresses start with "1" and represent the original format; SegWit addresses (also known as nested SegWit addresses) start with "3," offering better compatibility but only modest efficiency gains; native SegWit addresses use bech32 encoding and start with "bc1," delivering the highest efficiency and lowest transaction fees, making them the recommended format today.

For users seeking optimal efficiency and cost savings, native SegWit addresses (those beginning with "bc1") are highly recommended. These addresses not only maximize space utilization but also offer stronger error detection and an easy-to-read all-lowercase format.

05 Soft Fork Implementation Strategy

SegWit was implemented via a soft fork rather than a hard fork—a carefully considered technical decision. A soft fork ensures backward compatibility: nodes that haven’t upgraded can still validate and accept new blocks, though they can’t take advantage of the new features.

By contrast, a hard fork would create an incompatible new chain, requiring all users to upgrade their software and potentially fracturing the community and weakening network effects.

To activate SegWit, miners signaled support through the block version number. Once 95% of blocks in a sequence of 2,016 signaled support, the upgrade would be activated in the next adjustment period.

This consensus mechanism enabled a smooth network transition and avoided potential splits. As of August 2017, SegWit was successfully activated at block height 481,824.

06 Impact on Transaction Speed and Fees

SegWit’s most immediate benefits are felt in the transaction experience. By making more efficient use of block space, SegWit allows each block to include more transactions, easing network congestion.

During periods of high network activity, users with SegWit addresses typically enjoy lower fees and faster confirmation times.

Real-world tests show that, under similar network conditions, transactions using native SegWit addresses can cost 30% to 50% less than those using legacy addresses. For users who frequently transact in Bitcoin—especially those moving assets on platforms like Gate—the cumulative savings over time can be substantial.

07 Paving the Way for Second-Layer Solutions

SegWit is far more than an isolated upgrade; it opened the door for Bitcoin’s second-layer scaling solutions. The most notable is the Lightning Network, an innovative protocol enabling near-instant, ultra-low-fee Bitcoin micropayments.

The Lightning Network establishes off-chain payment channels, requiring on-chain transactions only when channels are opened or closed, dramatically reducing the load on the main network. Without SegWit’s fix for transaction malleability, the Lightning Network’s security model would have faced critical flaws.

Today, as the Lightning Network and other second-layer solutions mature, Bitcoin is gradually evolving from a pure store of value into a more efficient payment medium—a transformation fundamentally enabled by SegWit.

08 Adoption Status and Future Outlook

Since its activation in 2017, SegWit adoption has steadily increased. Most mainstream wallets and exchanges now support SegWit addresses, especially the native format.

By the end of 2025, over 80% of Bitcoin transactions use the SegWit format, reflecting broad community recognition of the upgrade.

On leading exchanges like Gate, users can freely choose among different Bitcoin address types for deposits and withdrawals. For the best transaction experience and cost efficiency, it’s recommended to use native SegWit addresses. As the Bitcoin ecosystem continues to evolve, SegWit’s importance will only grow, providing a solid technical foundation for further innovation.

Looking Ahead

Bitcoin’s price experienced a period of adjustment at the end of 2025. As of early 2026, market analysts remain divided in their price predictions for Bitcoin, with some forecasting a rally to $100,000 or even $150,000, while others remain more conservative.

Regardless of market fluctuations, ongoing advancements in Bitcoin’s core technologies—like SegWit—are quietly reshaping the underlying architecture of digital finance.