No, you do not need a MIDI keyboard to start learning piano. You can learn the note layout, rhythm, basic chords, melody, and the first steps of songwriting on a phone, tablet, computer keyboard, or acoustic piano. A MIDI keyboard becomes useful when you want physical keys to control music software. That is a workflow upgrade, not an entry ticket.
The confusion comes from treating three different things as if they were the same: learning music, learning piano technique, and controlling software.
What does a MIDI keyboard actually do?
A MIDI keyboard tells software which note you pressed, when, and sometimes how hard. Your phone or computer turns that data into sound.
MIDI itself makes no sound and teaches no lessons. A small controller can have excellent software integration and poor key feel. A digital piano can feel much closer to an acoustic instrument and happen to include MIDI as an extra connection. The socket tells you little about whether the keyboard is good for learning technique.
If you are shopping for keys, ask about size, resistance, and touch sensitivity before MIDI.
What can you learn without physical keys?
Quite a lot at the beginning.
A screen keyboard teaches where notes sit and how black-key groups organise the layout. A falling-note game trains timing and gives you a quick route into familiar songs. A chord tool can show which notes belong in C major, A minor, or a more unusual chord. Listening and copying melodies builds your ear wherever the notes come from.
At a laptop, the free browser piano maps computer keys to piano notes. It is good for checking a melody or learning the layout without installing anything. The free chord player is quicker when your question is "what does this chord sound like?"
These are real musical skills. They transfer. What does not transfer cleanly is touch.
When do physical keys become important?
Physical keys matter when your goal includes two-handed coordination, consistent fingering, dynamics, and control of tone. A flat screen cannot teach how deeply a key travels or how a quiet note feels different from a loud one. A computer keyboard cannot fit piano hand shapes.
Screen practice is not fake, just incomplete. Start with notes, rhythm, and simple songs, then add real keys once the habit justifies the purchase.
If acoustic technique is the destination, a weighted digital piano is a better long-term choice than a tiny unweighted MIDI controller. If portability and software control matter more, a compact MIDI keyboard may be exactly right.