Short answer. Article 355 lists writing, printing, lithography, engraving, radio, phonograph, painting, theatrical exhibition, cinematographic exhibition — and closes with "any similar means". That last phrase is what allows the article to reach forms of publication the 1930 drafters could not have imagined.
What the law says
A libel committed by means of writing, printing, lithography, engraving, radio, phonograph, painting, theatrical exhibition, cinematographic exhibition, or any similar means
Revised Penal Code, Article 355 — Libel By Writing Or Similar Means. Read the full provision →
A list that ends with an open door
The article covers a libel committed by means of writing, printing, lithography, engraving, radio, phonograph, painting, theatrical exhibition, cinematographic exhibition, or any similar means. Read the list and its age is obvious — lithography and the phonograph are not where modern disputes arise. The operative words are the last four. "Any similar means" is what carries the article forward: the common feature of everything named is that the defamatory matter is fixed in some durable or broadcast form and put before other people. A defamatory statement spoken face to face is oral defamation under a different provision; one that is written, recorded, broadcast or displayed falls here.
What the article does not supply
Article 355 is only the means provision. It does not define libel, and a complaint cannot be built on it alone. The definition sits in a separate article, and it requires a defamatory imputation of a crime, vice, defect or any act tending to dishonour or discredit a person; publication, meaning communication to at least one third person; identification of the person defamed, even indirectly; and malice. Truth alone is not automatically a defence either — the Code sets conditions on when proof of truth may be admitted, and certain communications are privileged. Anyone reading this article in isolation and concluding that an unflattering post is necessarily criminal has read only a quarter of the picture.
Online publication
This is the question most readers actually have. Defamatory material posted on the internet is not prosecuted under Article 355 by itself; a separate special law on cybercrime created an offence of libel committed through a computer system, drawing its definition from the Revised Penal Code but carrying a heavier penalty and its own procedural rules. A screenshot of a post is therefore not simply "Article 355 evidence" — which statute applies affects the penalty, the prescriptive period and where the case may be filed. If your complaint or your exposure concerns something posted online, that distinction is the first thing to get right, and it is worth specific advice rather than assumption.
Penalty, the civil action, and practical steps
The penalty is prisión correccional in its minimum and medium periods or a fine ranging from ₱40,000 to ₱1,200,000, or both. Those peso figures are current because Republic Act No. 10951 (2017) revised the fines and property values throughout the Revised Penal Code; older reproductions still print the 1930 amounts — for theft and estafa they show 12,000 and 22,000 pesos where the current figures run to millions — so check which version any source you rely on is giving you. The article also preserves the offended party's separate civil action for damages, which runs in addition to the criminal case. Practically: preserve the publication itself with dates and full context rather than a cropped screenshot, note who saw it, identify the author and anyone who republished it, and consult a lawyer promptly, because these actions prescribe quickly.