How can several programs download XML from Brazilian NF-e?

I believe the only legal way to do this is through the Federal Revenue Web Services available at Electronic Invoice Portal - Web Services .

I'm currently working on an NF-e system, and I already do both sending information and receiving (including NF-e XML) through Web Services, but for all operations done legally, you need the digital certificate data from the sender or recipient.

Without the digital certificate that can be either type A1 or type A3, there is no way to connect to the Revenue servers. If there is another legal form, I do not know and the IRS did not mention this in its Technical Notes.

The only legal way to do this is by using the IRS Web Services, performing authentication with the user's digital certificate.

The cool way to do this is by using direct communication with the Recipe API. This communication is done by webservices.

The nfephp website allows you to implement this on your own: link

If you do not have a domain in programming, you can use the Focus NFe API. But it's not free, but it allows you to get both XML and PDF from DANFE in a very practical way: link

One possibility is during the issue (authorization), to add a specific tag authorizing Cnpjs to download the XML.

This requires at least verbal authorization from the issuer.

One example is Admsis, which has a 100% web erp.

The issuer authorizes Admsis' Cnpj to download XML via web services or the national website.

The state department may not allow this, as is the case of SP.

Well, there is software called NF-e that lowers the XML from NF-e, CT-e, NFC-e without and with digital certificate. It also has option of downloading with and without the manifestation of the recipient the original XML. If needed, they offer integration with your system. Website: www.auxilionfe.com