BridgeHelper

BridgeHelper is a Forge 1.8.9 mod that shows you your speed-bridging timing in real time — while you're actually bridging, not after you've already fallen.

Configuration GUI Keybind: M

It reads your raw keyboard input to calculate exactly when you're hitting your placement window, with sub-tick accuracy.
That means the feedback you see is based on your real movement, not just what the game has processed yet. You can view the raw millisecond data or switch to simple plain-English messages depending on what you prefer.
If your bridging feels inconsistent but you can't figure out why, this mod is what you're missing. Silent trial-and-error is a slow way to build muscle memory - instant feedback isn't.
A few things to know before downloading:

Requires Minecraft Forge 1.8.9. Support for modern versions will be coming in the future.
Press M in-game to open settings and position your HUD
The mod only activates while you're actively bridging, so it won't clutter your screen otherwise