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Caddy vs Keil MDK

Caddy logo

Caddy

Cloud

Web server with automatic HTTPS by default

From
Free
Free plan
Yes
Full reviewWebsite
Keil MDK logo

Keil MDK

Developer Tools

Microcontroller Development Kit for Arm-based devices

From
Free
Free plan
Yes
Full reviewWebsite

The short version

  • Each has a real cost: Caddy smaller ecosystem than Nginx, so third-party guides and modules are fewer; Keil MDK pricing for Essential and Professional subscriptions not disclosed on primary site
  • Prices and features above were last checked on 29 August 2026.

Where they differ

Only the attributes on which Caddy and Keil MDK actually diverge.

Attributes where Caddy and Keil MDK differ
AttributeCaddyKeil MDK
Pricing modelOpen source, no licence feefreemium
PlatformsLinux, macOS, Windows, DockerWeb
CategoryCloudDeveloper Tools

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Caddy

  • Automatic HTTPS
  • Caddyfile
  • Reverse proxy
  • Single binary

Only in Keil MDK

Nothing recorded that Caddy does not also cover.

What people use each for

The jobs each tool is most often brought in to do.

Caddy

  • Sites and services where expired certificates have caused outages beforenot Keil MDK
  • Small deployments where Nginx configuration is more effort than the problem warrantsnot Keil MDK
  • Reverse proxying internal services with TLS without a certificate workflownot Keil MDK

Keil MDK

  • Embedded software developmentnot Caddy
  • ARM microcontroller programmingnot Caddy
  • Professional development environmentsnot Caddy

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Caddy

  • Smaller ecosystem than Nginx, so third-party guides and modules are fewer
  • Adding plugins means rebuilding the binary rather than loading a module
  • Under very high throughput Nginx generally still benchmarks ahead
  • Automatic certificate issuance needs outbound internet access, which complicates air-gapped deployments

Keil MDK

  • Pricing for Essential and Professional subscriptions not disclosed on primary site
  • Customers must contact Arm Developer Tools store for subscription rates

Pricing, plan by plan

Caddy

Free
  • CaddyFree
    • Full functionality
    • Commercial use permitted
    • Community support

Keil MDK

Free

No published plan breakdown. See the Keil MDK review.

Which should you pick?

Choose Caddy if

  • You need automatic https.
  • You want to start without paying.
  • You work on Linux, macOS, Windows, Docker.
  • You also want caddyfile.
Caddy review

Choose Keil MDK if

  • You want to start without paying.
Keil MDK review

Questions people ask

Is Caddy or Keil MDK better?
Neither clearly leads. Caddy starts at Free and Keil MDK at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Caddy or Keil MDK?
Caddy starts at Free and Keil MDK at Free.
Does Caddy or Keil MDK run on more platforms?
Caddy runs on Linux, macOS, Windows, Docker. Keil MDK runs on Web.
Can I use Caddy for free?
Both have a free tier, so you can try either at no cost before committing.
What is Caddy best used for?
Caddy is most often used for sites and services where expired certificates have caused outages before, small deployments where nginx configuration is more effort than the problem warrants, reverse proxying internal services with tls without a certificate workflow. Of those, sites and services where expired certificates have caused outages before and small deployments where nginx configuration is more effort than the problem warrants are not what Keil MDK is typically brought in for.
What can Caddy do that Keil MDK cannot?
Caddy covers Automatic HTTPS, Caddyfile, Reverse proxy, Single binary.

Answered from the vendors’ own pages

Caddy: Is Caddy free?

Yes, open source under the Apache 2.0 licence, free for commercial use.

Keil MDK: Does Keil MDK have a free version?

Yes, Keil MDK Community Edition is free for non-commercial projects. Essential and Professional editions are available as monthly or annual subscriptions.

Source
Caddy: What does automatic HTTPS mean?

Caddy obtains certificates from Let’s Encrypt or ZeroSSL on first request and renews them before expiry, with no cron job or configuration.

Keil MDK: How much do Keil MDK paid editions cost?

Specific pricing for Essential and Professional editions is not published on the main site. Rates are available from the Arm Developer Tools store or by contacting Arm sales.

Source
Caddy: Caddy or Nginx?

Caddy is dramatically simpler to configure and removes certificate management. Nginx has the larger ecosystem and better peak throughput.

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