When software developers and website builders want to test out their web-based components locally, ngrok is a popular option. For developers that would prefer a web-based testing solution that requires no installation, 
Serveo is a good solution.
In addition to the web-based solution above, some developers may find themselves more comfortable testing their products using open source alternatives to ngrok.
Bring your localhost servers on-line. PageKite is software that gives your localhost servers names and makes them globally visible. It works with any computer and any Internet connection. It's so easy you'll never want to think about routers, IP addresses or other technicalities again. It's open source, too!
Port forwarding service for exposing your local PC to Internet from behind firewall or without real IP address. Uses OpenVPN or SSH encrypted tunnel from localhost to Portmap.io.
An open source serveo/ngrok alternative. HTTP(S)/WS(S)/TCP Tunnels to localhost using only SSH.
beame-insta-ssl is open-source and free to use! It makes it easy for any web developer to make use of encryption - and get secure communications. beame-insta-ssl will get you your very own fully-qualified domain name under the beame subdomain that looks something like this: https://ypxf72akb6onjvrq.ohkv8odznwh5jpwm.v1.p.beameio.net/insta-ssl and your very own free SSL certificate (GlobalSign root CA). This will allow you to tunnel securely over HTTP.
LocalXpose is a reverse proxy that enables you to expose your localhost to the internet Features: • GUI & CLI • Unlimited connections • HTTP/s, TLS, TCP and UDP tunnels • Password protected tunnels • Custom subdomain • Custom domain • Custom TCP/UDP endpoint's port • Domains and endpoints reservations • Built-in file server • Built-in let's encrypt
Teleconsole is a free service to share your terminal session with people you trust. Your friends can join via a command line via SSH or via their browser over HTTPS. Use this to ask for help or to connect to your own devices sitting behind NAT. You can also forward local TCP ports to your friends. Use this feature to allow them access the web applications running on your localhost when you are behind NAT.
Beeceptor is a Rest API mocking tool. You can get started by defining endpoints and mock API paths. * Using Beeceptor, a mock API endpoint is up and ready to be consumed in seconds - in short, No Coding Required. Just define API path, response and start hitting from code. * Wrap an existing APIs endpoint with Beeceptor endpoint and inspect all the traffic going to original API. Helps in debugging headers and body for HTTP requests.
Packetriot makes it simple to expose services and data on local and private networks to the Internet. You can serve static websites, dynamic web applications, test single-sign-on work-flows or build webhooks. Developers and small businesses that use low-to-medium tier resources in public clouds can easily host those resources on their own equipment with their existing network connectivity. With Packetriot you can make any application, from any network, available to the Internet.
tmate is an instant terminal sharing software fork from tmux. Tmate can use as daemon, and you also can host your own server.
You can use inlets to connect HTTP and TCP services between networks securely. Through an encrypted websocket, inlets can penetrate firewalls, NAT, captive portals, and other restrictive networks lowering the barrier to entry. VPNs traditionally require up-front configuration like subnet assignment and ports to be opened in firewalls. A tunnel with inlets can provide an easy-to-use, low-maintenance alternative to VPNs and other site-to-site networking solutions.
