“The DOI (Digital Object Identifier) is an international standard (ISO 26324) managed by the International DOI Foundation, which provides a system to support persistent identification of content objects and related entities in digital networks.”

“You do not have to be a member of the DOI Foundation in order to assign DOI names but you do need to be affiliated with a Registration Agency in some way. DOIs are, and will always be, free to resolve. A DOI can apply to any form of intellectual property expressed in any digital environment. An entity can be identified at any arbitrary level of granularity. This means that, for instance, DOIs can identify a journal, an individual issue of a journal, an individual article in the journal, or a single table in that article”

• https://doi.org
• https://www.crossref.org/services/content-registration/
• https://www.doi.org/the-community/existing-registration-agencies/
• https://www.doi.org/the-identifier/resources/
• doi:10.1000/292
• etc

see crossref

• US based
• pricing https://www.crossref.org/fees/

see datacite

• based in Germany as e.v
• pricing Membership Fee of 2000€ and Service Fee of 500€ per year plus 0,80€ per DOI
• etc+

• mEDRA (multilingual European Registration Agency)
• a brand of ediSer, the service company of the Italian Publishers Association
• pricing (https://www.medra.org/en/terms.htm][details)
  • 150€ startup fee, 180–6000€ per year for 30–8000 DOIs (then 4.50 to 0.45 each)
  • additional 250€ for crossref integration (NB this is more expensive than crossref)
• guide https://www.medra.org/en/guide.htm

• not a registration agency but a Rotterdam Stichting that provides sponsored crossref membership in DOI blocks
• supports the dissemination of research content in the arts, architecture, built environment, and design domains.
• pricing from €19/yr for 5 DOIs to €99/yr for 50 (includes crossref membership).
• platforms are hosted in a climate neutral data centre by greenminihost at evoswitch -largest provider of Mac mini hosting in Europe
• CC-BY-4.0 licence for hosted content (but DOI users can also host content elsewhere)
• https://openaccess.ac/index.php/what-we-do/dois

• ONIX for DOI Metadata Schema v2.0

• https://datacite.org/blog/cool-dois/

• Once registered with crossref, you receive a DOI prefix, 10.XXXX
• Crossref provides a web deposit form that generates the xml
• Enter the basic metadata here (title, authors, publishers, date etc)
• And the DOI, which consists of your DOI prefix followed by a suffix which you generate yourself
• Suffixes must be unique, contain numbers and/or letters and -._;()/ are case-insensitive and ideally are short string, easily typed yet “dumb” meaning that they contain no obvious information. A best practice DOI would be 10.3390/s18020479
• On submitting the form, you are asked for your crossref login, and an email address where the deposit results should be sent.
• A DOI string can’t be changed once registered, and DOIs cannot be deleted.
• Once the DOI is confirmed you then create a landing page for the DOI.
• For the landing page it's usually enough to add the DOI information (title, author and/ DOI URL as an html link) at the top of the page of the referenced object, however if the item is a PDF it's advised to make a separate page.
• You also receive a copy of the xml. If changes need to be made to your metadata record, you can edit and submit the XML instead of re-entering your metadata into the form.
• Other metadata that might be added include funding an license metadata
• To add, change, or remove metadata from your existing records, you generally just resubmit your complete metadata record with the changes included.
• You can add funding and license metadata to multiple DOIs at once by uploading a csv file to the web deposit form using the supplemental metadata upload on crossref site.