Turns out, when we say 1MB in bitcoin, we really mean 1MB (not 1 MiB). 

I always thought it's using powers of 2 even though it's using MB instead of MiB.

Interesting! 

For those interested, the code for the soft fork in bitcoin core was merged in 

When github displays a code change it highlights any code that was removed in red and it highlights any code that was added in green. The code that was removed says this:

/** The maximum allowed size for a serialized block, in bytes (network rule) */
static const unsigned int MAX_BLOCK_SIZE = 1000000;

/** The maximum allowed size for a serialized block, in bytes (only for buffer size limits) */
static const unsigned int MAX_BLOCK_SERIALIZED_SIZE = 4000000;

Notice that the block size used to be 1 megabyte but it changed to 4 megabytes. Segwit definitely included a block size increase.

bitcoin

How segwit increased the block size without a hard fork

super_testnet

For those interested, the code for the soft fork in bitcoin core was merged in [this code change](https://github.com/bitcoin/bitcoin/commit/2b1f6f9ccf36f1e0a2c9d99154e1642f796d7c2b#diff-74d3d558e2ae1b1c967ea13d01ce15875cc7de50c93c26db73ccb3e4db5cfdacL6) in 2016.

When github displays a code change it highlights any code that was removed in red and it highlights any code that was added in green. The code that was removed says this:

```
/** The maximum allowed size for a serialized block, in bytes (network rule) */
static const unsigned int MAX_BLOCK_SIZE = 1000000;
```

The code that was added says this:

```
/** The maximum allowed size for a serialized block, in bytes (only for buffer size limits) */
static const unsigned int MAX_BLOCK_SERIALIZED_SIZE = 4000000;
```

Notice that the block size used to be 1 megabyte but it changed to 4 megabytes. Segwit definitely included a block size increase.