In addition to being done locally for a database, geocoding can be done as a web service from a server. The server might limit you to a specified number of requests per day, tracked by your IP address, and entice you to pay for more requests. This tracking can be fooled, and think you have exceeded your quota far earlier than it should. It may only complain every few records. For example http://www.gpsvisualizer.com/geocoder/ can use either the Yahoo or the Google service, but your browser will be the one making the request and running into the limit.Google geocoding now requires an account and an API key. You must have a credit card on file, but do get some free usage each month.
Google geocoding API uses requests like:
TIGER geocoding in MICRODEM.
Census Bureau online geocoding: https://geocoding.geo.census.gov/geocoder/locations/addressbatch?form
Last revision 3/25/2019