11 Best Software to Build Real-Time Applications

Direct answer: the research for this guide substantiates five real-time platforms: Firebase Realtime Database, Supabase Realtime, AWS AppSync, Ably, and PubNub. They solve different problems. Firebase synchronizes JSON database state, Supabase combines broadcast, presence, and Postgres changes, AppSync provides managed GraphQL subscriptions and WebSocket Pub/Sub, while Ably and PubNub focus on managed messaging. The available evidence does not support inventing six more products or claiming an objective ranking of eleven.

Choose the product by the kind of real-time behavior your application needs: synchronized application data, database change feeds, presence, chat, cursor or event broadcasting, or a managed API layer. Current prices, quotas, latency figures, and independent benchmarks were not verified in this research, so confirm those details on each vendor’s pricing and limits pages before committing.

What “real-time” means in an application

Real-time usually means clients receive a change without repeatedly polling an HTTP endpoint. The implementation can still be very different:

Database synchronization: clients subscribe to a shared data model and receive updates.
Database change feed: inserts, updates, and deletes are emitted as events.
GraphQL subscriptions: a managed API maintains live WebSocket connections for selected fields.
Pub/Sub messaging: publishers send events to channels and subscribers receive them.
Presence: clients publish ephemeral state such as online, typing, or cursor position.

A dashboard, multiplayer game, chat product, and collaborative editor can all be called real-time while requiring different guarantees. Decide whether events must be durable, whether users need offline edits, whether ordering matters, and how authorization is enforced.

At-a-glance comparison

Platform	Primary architecture	Best fit	Key caveat
Firebase Realtime Database	Cloud NoSQL JSON synchronization	Applications that want client SDKs, local persistence, and synchronized state	Consider Cloud Firestore when you need richer data models, queryability, scalability, or higher availability
Supabase Realtime	Broadcast, Presence, and Postgres Changes	Postgres-backed applications, custom events, presence, and dashboards	Use private channels and RLS in production; Presence has computational overhead; Postgres Changes is best for testing or low connected-user counts
AWS AppSync	Managed GraphQL subscriptions and WebSocket Pub/Sub	AWS teams that want a managed GraphQL or event API	GraphQL schema and AWS integration choices add design work
Ably	Managed Pub/Sub plus higher-level products	Event distribution, persistent connections, and products such as Chat	Choose the interface based on latency, connection needs, feature complexity, integrations, and pricing implications
PubNub	Managed publish/subscribe messaging	Cross-platform realtime messaging with vendor SDKs	This research did not validate comparative pricing, limits, or independent latency measurements

1. Firebase Realtime Database

Firebase Realtime Database is a cloud-hosted NoSQL database that stores JSON and synchronizes it across connected clients. Firebase documents local persistence and synchronization after a device reconnects. Access rules control reads and writes, and Firebase Authentication can be used with those rules.

Use it when

Your data fits a JSON-oriented model.
Clients should receive synchronized state with offline behavior.
You want Firebase client SDKs and security rules.

Watch for

Modeling nested JSON and complex queries can become difficult. Google directs teams toward Cloud Firestore for modern applications that need richer data models, queryability, scalability, or higher availability. Read the Firebase Realtime Database documentation before choosing.

import { initializeApp } from "firebase/app";
import { getDatabase, ref, onValue } from "firebase/database";

const app = initializeApp({
  apiKey: process.env.FIREBASE_API_KEY,
  authDomain: process.env.FIREBASE_AUTH_DOMAIN,
  databaseURL: process.env.FIREBASE_DATABASE_URL,
  projectId: process.env.FIREBASE_PROJECT_ID
});

const db = getDatabase(app);
const statusRef = ref(db, "rooms/room-1/status");

const unsubscribe = onValue(statusRef, (snapshot) => {
  console.log("status changed:", snapshot.val());
});

process.on("SIGINT", () => { unsubscribe(); process.exit(0); });

2. Supabase Realtime

Supabase Realtime provides three mechanisms:

Broadcast: low-latency messages and custom events.
Presence: shared ephemeral user state.
Postgres Changes: subscriptions to inserts, updates, and deletes.

Supabase recommends private channels with row-level security policies for production authorization. Its documentation warns that Presence has computational overhead and recommends Postgres Changes mainly for quick testing or low connected-user counts. See the feature guide and getting-started guide.

import { createClient } from "@supabase/supabase-js";

const supabase = createClient(
  process.env.SUPABASE_URL,
  process.env.SUPABASE_ANON_KEY
);

const channel = supabase
  .channel("private-room-1")
  .on("broadcast", { event: "cursor" }, ({ payload }) => {
    console.log("cursor:", payload);
  })
  .on("postgres_changes", {
    event: "INSERT",
    schema: "public",
    table: "messages",
    filter: "room_id=eq.room-1"
  }, (payload) => {
    console.log("new message:", payload.new);
  })
  .subscribe();

process.on("SIGINT", async () => {
  await supabase.removeChannel(channel);
  process.exit(0);
});

3. AWS AppSync

AWS AppSync provides managed GraphQL APIs with subscriptions that maintain secure WebSocket connections for live updates. AWS also documents AppSync Events, a WebSocket-powered Pub/Sub API available since March 13, 2025. AWS says AppSync manages subscription connections and scaling requirements. It is a strong architectural fit for teams already standardizing on AWS or GraphQL; that fit is an editorial inference, not a claim that it is automatically cheaper or simpler.

subscription OnMessageAdded($roomId: ID!) {
  messageAdded(roomId: $roomId) {
    id
    roomId
    body
    createdAt
  }
}

const query = `subscription OnMessageAdded($roomId: ID!) {
  messageAdded(roomId: $roomId) { id roomId body createdAt }
}`;

// Use your AppSync client or SDK to start this subscription.
// The client must authenticate according to the API's configured mode.
const variables = { roomId: "room-1" };
console.log({ query, variables });

Read the AppSync documentation and the realtime data guide for authentication, schema, and connection configuration.

4. Ably

Ably offers a core Pub/Sub service and higher-level products such as Chat. Its product guidance says the right interface depends on latency requirements, persistent connections, feature complexity, integration needs, and pricing implications. Treat Ably’s scale, reliability, and performance statements as vendor claims rather than independent benchmarks. Start with the platform overview and product guidance.

import Ably from "ably";

const client = new Ably.Realtime({ key: process.env.ABLY_API_KEY });
const channel = client.channels.get("room-1");

await channel.subscribe("message", (message) => {
  console.log(message.data);
});

await channel.publish("message", { body: "hello" });

Keep API keys on a server and issue appropriately scoped client credentials. Define whether events are transient or need history before selecting channels and retention behavior.

5. PubNub

PubNub documents SDKs and publish/subscribe messaging for realtime applications across devices and platforms. It is a managed messaging candidate when you want vendor SDKs instead of operating WebSocket infrastructure yourself. The available evidence does not establish a comparative ranking, current pricing, limits, or measured latency. Consult the official PubNub documentation.

import PubNub from "pubnub";

const pubnub = new PubNub({
  publishKey: process.env.PUBNUB_PUBLISH_KEY,
  subscribeKey: process.env.PUBNUB_SUBSCRIBE_KEY,
  userId: "user-1"
});

pubnub.addListener({
  message: (event) => console.log("message:", event.message)
});

pubnub.subscribe({ channels: ["room-1"] });
await pubnub.publish({ channel: "room-1", message: { body: "hello" } });

How to choose among the five

Question	Likely direction
Is synchronized JSON state and offline persistence the main need?	Evaluate Firebase Realtime Database.
Is Postgres already the source of truth?	Evaluate Supabase Realtime, while planning authorization and connection volume carefully.
Do you need GraphQL subscriptions or AWS-managed WebSocket APIs?	Evaluate AppSync.
Do you need a dedicated messaging layer, presence, or chat abstractions?	Compare Ably and PubNub against your event model and SDK requirements.
Must updates survive reconnects?	Verify persistence, replay, ordering, and offline semantics; do not infer them from the word “realtime.”

Architecture checklist before production

Define event types, payload schemas, maximum payload size, and versioning.
Choose durable data versus ephemeral events.
Specify ordering, duplication, and replay behavior.
Authorize every channel, room, topic, or database row.
Handle reconnects with backoff and resynchronization.
Measure active connections, messages, fan-out, bandwidth, and delivery failures.
Load-test the busiest room and the worst reconnect storm.
Review each vendor’s current pricing and quotas for your traffic pattern.

Performance, reliability, and cost considerations

Connection count alone does not describe cost or capacity. A quiet connection, a high-frequency cursor stream, and a broadcast to thousands of subscribers create very different workloads. Track messages sent, messages delivered, fan-out, connection minutes, database reads, and bandwidth according to the provider’s billing model.

Use throttling or sampling for cursor and typing events. Batch durable writes where the product permits it, keep transient events out of the primary database, and unsubscribe when a view is hidden. Add client-side sequence numbers or timestamps when consumers must detect gaps or stale updates.

Reconnect logic should use exponential backoff with jitter, clear stale subscriptions, and fetch authoritative state after reconnecting. Assume duplicate delivery is possible unless the selected service explicitly documents stronger guarantees; make handlers idempotent.

Troubleshooting

Clients connect but receive no events

Check that the client subscribed to the exact channel or topic, that the publisher used the same name, and that authorization permits the subscription. For database products, verify the table, path, filter, and replication or change-feed configuration.

Events arrive twice

Inspect reconnect handlers and component lifecycles for duplicate subscriptions. Remove old listeners before adding new ones and make event processing idempotent.

Updates stop after sleep or network changes

Mobile and laptop networks routinely suspend sockets. Reconnect with backoff, resubscribe, and request a fresh snapshot or replay from the last known sequence.

Presence becomes expensive or slow

Presence often creates more coordination work than ordinary broadcast. Publish less frequently, remove stale members, and follow Supabase’s guidance to use Presence minimally.

Database changes overwhelm clients

Filter events by room or tenant, project only required fields, aggregate high-frequency writes, and move ephemeral interactions to broadcast messaging.

Unauthorized data is visible

Do not rely on obscured channel names. Enforce authentication and authorization at the provider’s rules, RLS policies, resolver, or token layer, and test both allowed and denied subscriptions.

Or skip the browser setup

If your real-time product needs screenshots of dashboards, status pages, or collaboration views, ScreenshotNeo is the alternative to try first. It captures a URL with one request, removes cookie banners, newsletter popups, and chat widgets before the shot, and bills only clean shots. Bot checks, blank pages, timeouts, failed loads, and cache hits are not billed, and response headers identify the verdict and billing result. Its MCP server lets Claude, Cursor, and other MCP clients call take_screenshot, get_page_info, and capture_pdf.

See the ScreenshotNeo API documentation for all options.

curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webp

import requests
r = requests.get("https://api.screenshotneo.com/v1/shot", params={"access_key": "YOUR_API_KEY", "url": "https://stripe.com"}, timeout=90)
open("shot.webp", "wb").write(r.content)

const q = new URLSearchParams({ access_key: 'YOUR_API_KEY', url: 'https://stripe.com' });
const res = await fetch(`https://api.screenshotneo.com/v1/shot?${q}`);

Every plan includes the full feature set: full-page and element capture, device presets, retina scale, custom CSS and JavaScript, waits, request blocking, cookies and headers, PDFs, caching, signed links, async webhooks, bulk capture, and a usage API. The Free plan includes 1,000 screenshots each month with no card; paid plans start at $5 for 3,000. Create a free ScreenshotNeo account.

FAQ

Which option is a database and which is messaging?

Firebase and Supabase can synchronize or expose database-backed state. Ably and PubNub are managed messaging platforms. AppSync provides a managed GraphQL and Pub/Sub API layer.

Do I need WebSockets myself?

All five services abstract some or all connection handling, but your client still needs subscription lifecycle, authentication, reconnect, and state-reconciliation code.

Is there a proven best platform?

No. The available research supports five candidates but no independent head-to-head benchmark or objective winner.

Where are the other six products?

This guide does not fabricate them. Additional research is required before six more products can be described with comparable evidence.

Should every event be written to a database?

No. Persist business state that must be recovered; use ephemeral broadcast for interactions such as cursors or typing indicators when durability is unnecessary.