Check your own Portuguese
Write or paste a Portuguese text. This page holds it up against exactly the rules the site itself teaches: 27 constructions Portuguese does not have, 21 forms this site writes the European way, 68 irregular verbs conjugated as if they were regular, and 47 false friends. Each finding comes with the page on which the rule is explained. Everything runs in your browser; the text never leaves your device.
A closer look pays off.
What it is measured against
Every rule in this checker is on one of these pages — and the same table checks this site’s own Portuguese when it is built. A finding without a source would be an assertion; here are the sources, even without you checking anything.
What this checker can do — and what it cannot
It does not check your Portuguese. It checks 163 particular things in it. A text with no findings is not a text without mistakes: tenses, word order, articles and everything there is no rule for here are invisible to this tool. The reverse holds, though: whatever it reports is explained on a page of this site.
Three levels of certainty, and the difference matters. A mistake is a construction this site explicitly rules out — there is nothing to weigh up. A spelling is not a mistake but a choice that has to be kept: ônibus and autocarro are both correct, and estou trabalhando is not a wrong sentence — it is Brazilian, the way elevator is American, and this site writes European Portuguese throughout. A hint is a question rather than a verdict: constipado is a perfectly good Portuguese word — it just means that you have a cold, and whoever wrote it may have meant exactly that.
The Conjuntivo, the choice between pretérito perfeito and imperfeito, and where the object pronoun goes are left out on purpose. They cause more mistakes than anything else, and none of them can be spotted by a pattern: for the Conjuntivo the checker would have to understand the sentence, for the tenses it would have to know whether you are telling a story or describing a scene, and whether -me goes before or after the verb is decided by a word somewhere further back. They have pages of their own; here the checker says nothing about them.
The word list below is information, not a mark. It shows which levels the words of your text sit at in this vocabulary. A text made entirely of words from the first level can be very good, and one full of words from the top levels very bad.