Gurmukhi vs Shahmukhi: one language, two scripts
Punjabi is one spoken language written in two unrelated scripts. In Indian Punjab and most of the diaspora it is written in Gurmukhi, a left-to-right script developed in the 16th century. In Pakistani Punjab, home to the majority of the world's Punjabi speakers, it is written in Shahmukhi, a right-to-left script adapted from the Perso-Arabic alphabet. Same sentences, same songs, mutually unreadable on paper.
Where the split comes from
Shahmukhi ("from the king's mouth") grew out of the Persian script used by court administration long before partition. Gurmukhi ("from the Guru's mouth") was standardized by Guru Angad, the second Sikh Guru, in the 1500s to write the language people actually spoke, and it is the script of the Guru Granth Sahib. The 1947 partition hardened the geography: India's Punjab standardized on Gurmukhi in schools, Pakistan's on Shahmukhi. The language stayed one; the page split in two.
How different are they in practice?
Completely, as writing systems. Gurmukhi runs left to right, gives each of its 35+ letters one sound, and writes vowels explicitly with signs. Shahmukhi runs right to left, connects its letters cursively, and like Arabic script usually leaves short vowels unwritten, so the reader supplies them from context. Gurmukhi is generally the easier script to learn to read accurately for exactly that reason: what is written is what is said. A literate Punjabi speaker from Lahore and one from Ludhiana can talk for hours and be unable to read each other's texts.
Which should a learner start with?
Follow your people. If your family is from Indian Punjab, is Sikh, or you want to read the Guru Granth Sahib, learn Gurmukhi. If your family is from Pakistani Punjab, Shahmukhi connects you to your side of the border, and knowing Urdu script already gets you most of the way there. If you have no side, Gurmukhi is the practical pick for a learner: it is phonetic, most learning materials for English speakers use it, and most of the diaspora's songs, subtitles, and gurdwara classes do too.
Where Ladoo stands
Ladoo teaches Gurmukhi, and does not currently teach Shahmukhi. That is an honest limit of the app today. The spoken Punjabi it teaches is the same language on both sides of the border, so the speaking and listening work transfers completely; only the reading is script-bound. If Shahmukhi literacy is your goal, pair spoken practice with a Shahmukhi primer or a tutor.
Common questions
Can Gurmukhi readers read Shahmukhi?
Not without separately learning it. The scripts share no letterforms and run in opposite directions. The spoken language underneath is the same, so vocabulary transfers even though reading does not.
Which script do more people use?
Shahmukhi, by population: Pakistani Punjab has more Punjabi speakers than Indian Punjab and the diaspora combined. Gurmukhi dominates published learning materials, Sikh religious text, and the Indian and diaspora media most heritage learners grew up around.
Is one script older?
The Perso-Arabic tradition behind Shahmukhi is older as a writing system, but both have been used for Punjabi for centuries. Gurmukhi was standardized for Punjabi specifically in the 1500s, which is why it fits the language's sounds so tightly.
Keep going: the Gurmukhi alphabet chart · the vowel signs · the heritage speaker guide
Learn the whole script in the app. The Gurmukhi track goes from zero to reading, with tracing on every letter, and every lesson is free.