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APIs · head to head

Ably vs curl

Ably logo

Ably

APIs

Realtime data delivery platform for pub/sub messaging at scale

From
Free
Rated
-
Full reviewWebsite
curl logo

curl

APIs

Command-line tool for transferring data using URLs with wide protocol support

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Ably standard and Pro plans layer usage-based charges for messages, connection minutes, and data transfer on top of the base subscription, adding cost complexity.; curl open-source with no vendor pricing: curl is free and open-source under GPL 3.0; no subscription or licensing costs apply
  • They diverge on capability: Ably covers Pub/sub messaging, curl covers HTTP/HTTPS.
  • Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which Ably and curl actually diverge.

Attributes where Ably and curl differ
AttributeAblycurl
Pricing modelfreemiumopen-source
Platformsweb, ios, android, apiLinux, MacOS, Windows, Unix, Mobile
FoundedUnknown1997

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

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 Ably

  • Pub/sub messaging
  • Presence
  • Message persistence
  • Multi-protocol support
  • Encryption
  • Datadog integration

Only in curl

  • HTTP/HTTPS
  • FTP
  • Multiple protocols
  • Universal compatibility
  • Scripting tools
  • Linux support
  • MacOS support
  • Windows support

What people use each for

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

Ably

  • Building realtime chat or collaborative appsnot curl
  • Delivering live data feeds like stock prices or sports scoresnot curl
  • Broadcasting notifications to many concurrent clientsnot curl
  • Running mission-critical realtime infrastructure with high uptime SLAsnot curl

curl

  • API Developmentnot Ably
  • API Gatewaynot Ably
  • API Testingnot Ably
  • API Documentationnot Ably
  • Microservicesnot Ably

Where each one falls short

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

Ably

  • Standard and Pro plans layer usage-based charges for messages, connection minutes, and data transfer on top of the base subscription, adding cost complexity.
  • The jump from Standard ($29/month) to Pro ($399/month) is steep for teams needing more than 10k connections but not full Pro capacity.
  • 24/7 mission-critical support and 99.999% uptime SLAs are reserved for the custom-priced Enterprise tier.

curl

  • Open-source with no vendor pricing: curl is free and open-source under GPL 3.0; no subscription or licensing costs apply
  • Commercial support costs hidden: site references 'commercial support available' but pricing is not detailed or accessible from homepage
  • No SaaS model: curl is a command-line tool and library; costs are limited to optional commercial support contracts (pricing unknown)
  • Self-support burden: free software means customers rely on community forums or undisclosed commercial support pricing

Pricing, plan by plan

Ably

Free
  • FreeFree
    • 200 concurrent connections
    • 500 messages/second
    • 6M messages/month
  • Standard$29/month
    • 10k concurrent channels
    • 10k concurrent connections
    • 2.5k messages/second
  • Pro$399/month
    • 50k concurrent channels
    • 50k concurrent connections
    • 10k messages/second

curl

Free
  • Open SourceFree
    • Full curl functionality
    • Community support

Which should you pick?

Choose Ably if

  • You need pub/sub messaging.
  • You want to start without paying.
  • You work on web, ios, android, api.
  • You also want presence.
Ably review

Choose curl if

  • You need http/https.
  • You want to start without paying.
  • You work on Linux, MacOS, Windows, Unix, Mobile.
  • You also want ftp.
curl review

Questions people ask

Is Ably or curl better?
Neither clearly leads. Ably starts at Free and curl at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Ably or curl?
Ably starts at Free and curl at Free.
Does Ably or curl run on more platforms?
Ably runs on web, ios, android, api. curl runs on Linux, MacOS, Windows, Unix, Mobile.
Can I use Ably for free?
Both have a free tier, so you can try either at no cost before committing.
What is Ably best used for?
Ably is most often used for building realtime chat or collaborative apps, delivering live data feeds like stock prices or sports scores, broadcasting notifications to many concurrent clients, running mission-critical realtime infrastructure with high uptime slas. Of those, building realtime chat or collaborative apps and delivering live data feeds like stock prices or sports scores are not what curl is typically brought in for.
What can Ably do that curl cannot?
Ably covers Pub/sub messaging, Presence, Message persistence, Multi-protocol support. curl covers HTTP/HTTPS, FTP, Multiple protocols, Universal compatibility.

Answered from the vendors’ own pages

Ably: What does Ably cost?

Ably offers a free plan with 200 concurrent connections, a Standard plan at $29/month plus usage, a Pro plan at $399/month plus usage, and custom Enterprise pricing with unlimited channels and connections.

Source
curl: How much does curl cost?

curl is free and open-source software under the GPL 3.0 license. There is no cost to download, use, or modify the software.

Source
Ably: Is there a free plan, and what are its limits?

Yes, the free plan includes 200 concurrent connections, 500 messages per second, and 6 million messages per month with community and best-effort email support.

Source
curl: Is commercial support available for curl?

Yes. The curl website references 'commercial support available,' but pricing and details are not disclosed on the homepage and require visiting the support page.

Source
Ably: How is usage metered?

Beyond plan limits, Ably charges usage-based rates of $2.50 per million messages, $1.00 per million connection minutes, $1.00 per million channel minutes, and $0.25 per GiB of data transfer, with volume discounts available.

Source
curl: Can I sponsor curl financially?

Yes. The curl website offers an option to 'Sponsor curl financially.' Visitors can donate to support curl development, but the donation link must be accessed through the site's support section.

Source
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