The Space Devs API
The Space Devs (thespacedevs.com) has 2 public methods: get launch by mission or rocket name and list upcoming launches. Each costs 1 credit per completed run (1¢ with pay as you go); failed runs are free.
Unofficial. Not affiliated with or endorsed by The Space Devs.
Methods
2Finds a launch by mission or rocket name. Picks the next upcoming match, otherwise the most recent past match, and returns its details.
Returns mission, rocket, provider, status, result, times, site, orbit, landing, webcast, image, page link
Readthespacedevs.com/get_launchLists upcoming rocket launches worldwide, with launch windows in UTC and local site time. Results can be filtered by company, country or launch site.
Returns mission, rocket, company, status, UTC and local windows, site, pad, orbit, links
Readthespacedevs.com/list_upcoming_launches