Remember that most images you find on the Web are not public domain, even if they list no explicit copyright information. Images only qualify as being in the public domain if they fall under certain specific categories described below – images ineligible for copyright protection, very old works, works by certain government employees, and works where an explicit disclaimer of copyright has been made in writing by the author.

For a simple chart on US Public Domain regulations (Wikipedia servers are located in the US and fall under US guidelines) see the chart here.

General

((PD-OldOS)): for maps and sections of maps taken from Ordnance Survey (OS; Great Britain) maps over 50 years old (currently by 1973)
((PD-EU-no author disclosure)): for images published more than 70 years ago (currently by 1953) without an attached claim of authorship
((PD-ineligible)): for images that are inherently ineligible for copyright protection because they are based exclusively on common knowledge with no element of creativity. An example would be Image:F Major key signature.png or things like multiplication tables. If you have any doubts, please ask
((PD-old-100)): for images where the author died more than 100 years ago (currently in 1923 or earlier). (Note: not where the work, image, or subject is 100 or more years old)
((PD-US-expired)): for images published in the U.S. before 1929
- ((PD-US)): for some other cases
((PD-US-expired-abroad)): for images first published outside of the U.S. before 1929
- For images of pre-1929 foreign postage stamps use ((Stamp-PD-US-1923-abroad))
((PD-URAA)): for images first published outside of the U.S. from 1929 to 1977 (inclusive), but PD in the foreign source country on January 1, 1996. For the precise rules, see the template text
((PD-old-70)): for images where the author (e.g., photographer, painter, graphic artist) died more than 70 years ago (currently by 1953) (Note: not where the work, image, or subject is 70 or more years old.)
((Stamp-PD-US-1923-abroad)): for images of postage stamps first published outside of the U.S. before 1929 and therefore PD in the U.S.
((PD-US-1989)) Works published in the U.S. between 1978 and March 1, 1989, without a copyright notice, and where the copyright was not later registered
((PD-US-no notice)): for images published in the United States prior to 1978 without explicit notice of "copyright, year, owner" or "©" attached
((PD-US-not renewed)): for images published in the United States prior to 1964 for which copyright was not renewed within 28 years of the date of publication
((PD-anon-expired)): for images published anonymously outside the United States prior to 1929. Takes an optional parameter indicating the year of publication.
((PD-shape)): for images that only contain one very simple geometric shape
((PD-simple)): for images that only consists of typefaces, individual words, slogans, or simple geometric shapes
((PD-chem)): for images comprising conventionally drawn chemical structural formulae
((PD-logo)): for images of logos that consist of only typefaces, individual words, slogans, or simple geometric shapes

Dedications

These tags are used for an author to attempt to release their work into the public domain, disclaiming any copyright. See Wikipedia: Granting work into the public domain.

((PD-link)): a statement intended to release a contributor's own work into public domain and request an entirely optional link back to Wikipedia from anyone reproducing it
((PD-self)): a statement intended to release a contributor's own work into public domain
((PD-user|username)): a statement intended to release a particular user's own work into public domain by a Wikipedian. For Wikipedians not on the English Wikipedia, use ((PD-user|username|language code)) where the language code is the two-character ISO 639-2 code (lowercase) that corresponds to the language of the Wikipedia where the user has an account.
((PD-retouched-user|username)): remarking that a previous PD work has been digitally enhanced, and re-released into public domain by a Wikipedian.
((PD-author|name)): stating that the work is released into the public domain by its author, whose name is given

Art

((PD-art)): for images of 2-D (flat) works of art where the artist died more than 100 years ago.
- ((PD-art-life-70)): for images of 2-D (flat) works of art where the artist died more than 70 years ago.
- ((PD-art-US)): for images of 2-D (flat) works of art published prior to January 1, 1929.
- ((PD-art-3d)): for images of 3-D works of art where the artist died more than 100 years ago. This license ONLY covers the work of art. Photographic reproductions of 3-D objects attract their own copyright, therefore the appropriate image licensing tag should be used in addition.

Intergovernmental

((PD-Hubble)): for public domain images from the NASA/ESA Hubble Space Telescope as described on Hubblesite and Esahubble
((PD-USGov)): For works produced by an employee of the United States federal government in the performance of his or her duties. This blanket exemption does not apply to content published by other American governments, such as state, county, or city governments, who generally hold copyright unless they disclaim it; see Category:United States state public domain copyright templates for information on those that do.
- ((PD-CAGov)): All publicly released documents by agencies of the State of California (per California law)
- ((PD-FLGov)): See Copyright status of work by the Florida government
((PD-laws)): There is an exception to the above. Edicts of government, such as judicial opinions, administrative rulings, legislative enactments, public ordinances, and similar official legal documents are not copyrightable for reasons of public policy. This applies to such works whether they are Federal, State, or local as well as to those of foreign governments.
((PD-US-patent)): In general, the text and images of United States patents are not copyrighted.[1] In specific cases, patent applicants and holders may claim copyright in portions of those documents. Such applicants are required to identify the portions that are protected under copyright, and are additionally required to state the following within the body of the application and patent:[2] [3]

Other countries

Whenever an image is tagged using one of these tags, the image description page should also contain some rationale as to whether and why the image is presumed to be in the public domain in the U.S. and other countries. See also ((PD-US-1996)), which can be used to state that the copyright on the image was not restored by the URAA.

((PD-AR-Photo)): for photographs first registered in Argentina over 25 years ago. (Law 11.723, Article 34)
((PD-Albania)): for works whose author died at least 70 years ago, or for joint works created or published more than 70 years ago.
- ((PD-Albania-exempt)): For works exempt from copyright protection under Albanian law as per tag text.
((PD-Australia)): for published photographs whose creator died at least 70 years ago, or photographs taken prior to 1955.
- ((PD-AustraliaGov)): for works published by the Australian government or held under Crown Copyright in Australia more than 50 years ago.
((PD-Bangladesh)): for photographs published in Bangladesh over 60 years ago.
((PD-BrazilGov)): for "Brazilian official symbols", i.e. flags and symbols.
((PD-Canada)): for works that have fallen into the public domain in Canada under the Copyright Act of Canada.
- ((PD-CanadaGov)): for works by the government of Canada that have fallen into the public domain in Canada
((PD-China)): for photographs taken in China over 50 years ago, or for non-photographic images whose author died more than 50 years ago.
((PD-Croatia)): for works whose author died at least 70 years ago, or for joint works created or published more than 70 years ago, or works under the Agreement on Yugoslav succession issues of Vienna of 29 June 2001, see below ((PD-Yugoslavia)).
((PD-CzechGov)): for state symbols and symbols of other self-governing units.
((PD-Ethiopia)): for works first published in Ethiopia that have fallen into the public domain in Ethiopia.
((PD-GermanGov)): for statutes, ordinances, official decrees or judgments issued by a German federal or state authority, or court
((PD-GreekGov)): for official legislative, administrative or judicial documents issued by the Greek Government.
((PD-HK)) for images and photographs taken in Hong Kong whose author died more than 50 years ago, or works of unknown authorship published over 50 years ago.
((PD-Japan)): for works published in Japan where all authors died 50 years ago, or if the authors are not known, where the works were published over 50 years ago.
((PD-India)): for photographs, audio and videos first published by Indian citizens or the Indian government (and international organisations, per section 29) more than 60 years prior to January 1 of the current year (i.e., as of 2012^[update], published prior to 1 January 1952^{[needs update]}); see Indian Copyright Act, §§ s:Indian Copyright Law#CHAPTER V : TERM OF COPYRIGHT|25-27.
((PD-Iran)): for works first published in Iran where all the authors have died more than 30 years ago, or photos or movies first published in Iran and published more than 30 years ago.
((PD-Iraq)): for works first published in Iraq that have fallen into the public domain in Iraq.
((PD-Ireland)): for works first published in the Republic of Ireland where all the authors died over 70 calendar years ago, or if the authors are not known, where the works were published over 70 calendar years ago.
((PD-Israel-Photo)): for photographs taken in Israel or the British Mandate of Palestine over 50 years ago.
((PD-Italy)): for photographs taken in Italy over 20 years ago, or artistic photos taken over 70 years ago.
((PD-Lebanon)): For a work that is a photographic or cinematographic work and fifty years have elapsed since the end of the year of production, or is another type of work and fifty years have elapsed since the end of the year of the death of the author.
((PD-LithuaniaGov)): Republic of Lithuania Law on Copyright and Related Rights says: "Copyright shall not apply to official State symbols and insignia (flags, coat-of-arms, anthems, banknote designs, and other State symbols and insignia)."
((PD-Netherlands)): for
- works published in the Netherlands, Dutch East Indies, or Netherlands New Guinea over 70 years after the first January 1 following the work's publication and
- works published more than 70 years after the first January 1 following the author's death.
((PD-NZ)): for works made in New Zealand whose author died more than 50 years ago.
((PD-Pakistan)): for photographs published in Pakistan over 50 years ago, or for non-photographic images whose author died more than 50 years ago.
((PD-Philippines)): for works whose copyrights have already expired, that have been released into the public domain, or that are ineligible for copyright as stated by Philippine copyright law.
- ((PD-PhilippinesPubDoc)): for official public documents (or portions thereof) made in the Philippines of a legislative, administrative or judicial nature.
((PD-Poland)): for Polish photographs published in Poland without a copyright notice prior to May 23 1994.
((PD-PolishGov)): for Polish government documents, materials, signs and symbols.
((PD-ROC-GOV)): For works of the ROC Government under the terms of Article 9 of the Copyright Act of the Republic of China.
((PD-RomaniaGov)): for Romanian state symbols and symbols of public authorities and organisations, and for Romanian currency.
((PD-RU-exempt)): exempt from copyright protection under the Russian law as per tag text.
((PD-SerbiaGov)): for Serbian government documents, materials, pictures, etc.
((PD-Serbia)): for works whose author died before 1954 or, if anonymous, that were published before 1954 (public domain prior to introduction of the new law in 2004).
((PD-South-Africa)): For works published in South Africa that are more than 50 years old.
((PD-South Korea)): For works published in South Korea whose most recently deceased creator died more than 50 years ago.
((PD-Sweden)): for public domain images taken by Swedish photographers before 1944
((PD-Thailand)): for works whose copyright has expired in Thailand.
- ((PD-TH-exempt)): for works exempt from copyright protection under Thai law as per tag text.
((PD-Trinidad-and-Tobago)): for public domain images fifty years after the death of the photographer as per the Trinidad and Tobago Copyright Act, Part III, Section 19(1).
((PD-UA-exempt)): exempt from copyright protection under Ukrainan law as per tag text.
((PD-UK)): for works published in the United Kingdom that have fallen into the public domain in the United Kingdom.
- ((PD-BritishGov)): for images created by the British Government and published prior to 1956.
((PD-VenezuelaGov)): for "Venezuelan official symbols" i.e. flags and symbols.
((PD-Yugoslavia)): exempt from copyright protection by the Agreement on succession issues; Bosnia and Herzegovina, the Republic of Croatia, the Republic of Macedonia, the Republic of Slovenia and the Federal Republic of Yugoslavia, being in sovereign equality the five successor States to the former Socialist Federal Republic of Yugoslavia, have agreed in Vienna on 29th of June 2001. The Agreement came into force on 2004-03-25. [4] Note: must be used in conjunction with ((PD-Croatia)), see above.

Other

((PD-US-alien property)): for copyrights administered by the Alien Property Custodian
((PD-Bain)): for images from the Bain collection of the Library of Congress
((PD-Harris-Ewing)): for images from the Harris & Ewing collection of the Library of Congress
((PD-OpenClipart)): for images from the Open Clipart Library
((CopyrightedFreeUse-Link)): The image is free to use for any purpose, but requests an entirely optional link back to either Wikipedia or another site.
((PD-because)): for public domain images with a special reason. Use the format ((PD-because|reason)).
((PD-signature)): files displaying people's signatures thought to not be copyright in the US or the country of individual concerned.

New Zealand government

Publications of the New Zealand government are mostly covered by Crown copyright, which in New Zealand has a 100-year term under Section 26(3)(b) of the Copyright Act 1994. This puts most recent material out of bounds. However, there is an exception to these provisions for some documents:

((PD-NZSection27)): for works created by some New Zealand government entities, which are covered by Section 27(1) of the Copyright Act 1994 [5]. The section excludes from copyright protection the following NZ works: Bills, Acts, regulations, municipal bylaws, Hansard, select committee reports, court judgments, Royal commission reports, commission of inquiry reports, ministerial inquiry reports and statutory inquiry reports. Note that sourcing these from a third party provider that, say, annotated Acts, is dangerous – they would have copyright in those annotations, and/or copyright in a new typographical arrangement [6].

New Zealand Crown copyright used to only last 50 years, and copyright has expired for government works from 1944 or earlier. Regular copyright provisions (such as a 50-year term) apply to works by Crown entities and state-owned enterprises, not Crown copyright.

Deprecated (no longer being used)

((PD-Russia)): Used for works that were public domain under the Russian copyright law of 1993. Obsolete as of 1 January 2008 due to new Russian legislation.