Identity Tokens Explained: Best Practices for Better Access Control

Identity tokens—particularly JSON Web Tokens (JWTs) and OpenID Connect tokens—can be considered the backbone of modern application security, as they enable most of the authentication solutions we’ve come to rely on.

They also allow the delegation of authentication between identity management, provisioning services, and your authentication solution of choice.

While there’s no doubt identity tokens are a remarkable innovation with important uses, they also have limitations we can’t ignore.

I’ve seen folks try to shove way too much data into them or treat them as a single solution for both authentication and authorization—and that’s a recipe for disaster when you consider how these tokens actually work in practice.

Identity tokens are typically added to requests via headers (often an Authorization header or sometimes in cookies), and they have a limited capacity for storing claims. Moreover, if you rely on them for authorization in a direct sense, you’ll find yourself in trouble from both a performance and security standpoint.

This article will walk through what identity tokens are, the types of tokens you might encounter, and why you need to decouple authentication from authorization. It will also cover best practices for using and securing these tokens, offer use cases, and provide a FAQ section for quick reference.

Before we dive in, if you're looking for a flexible, production-grade authorization platform that keeps policy separate from identity, check out Permit.io.

Sign up for free, and see how we can help you handle fine-grained authorization, dynamic policies, and access control — without overloading your tokens.

Without further adieu, let’s talk about identity tokens:

What Are Identity Tokens?

First off, when I say “identity tokens,” I’m referring to tokens intended to represent some form of identity—either a human user or a machine identity—within your software ecosystem. They’re basically a packet of information generated by an identity provider or authentication service, which your application or service can then validate.

A common approach is to rely on a protocol such as OpenID Connect or OAuth 2.0 to manage these tokens. In these cases, the tokens can be short strings that encode vital identity details. If you’re using JSON Web Tokens, for example, that short string might be a base64-encoded piece of data that includes the header, payload (with claims about the user or machine identity), and a signature to confirm authenticity.

An interesting thing about identity tokens is how they let you delegate trust. When a user logs in through an identity provider, you don’t need to handle that user’s credentials directly. You can simply trust the identity token the provider generates, assuming you validate its signature. That’s quite the advantage for security because it reduces the exposure to raw credentials like passwords.

However, they’re far from all-encompassing, and if you try to cram every piece of user-related information into one token, you’re gonna have a bad time. I’ve worked with customers who attempted to map entire sets of permissions or even entire sets of URLs into a single token as claims.

This approach leads to major security problems and severely limits how you can update your software or your policies, as you tie everything together in a single artifact.

Types of Identity Tokens

Most common tokens fall under a couple of categories (although more specialized formats exist):

JSON Web Tokens (JWTs):

These are extremely popular. They usually contain standard fields in their payload, like an iss (issuer), exp (expiration), sub (subject), and possibly custom claims such as roles or scopes. They’re signed using a cryptographic algorithm (like RS256 or ES256), which gives them integrity so that recipients can verify the data hasn’t been tampered with.

JWT Structure Diagram

OpenID Connect Tokens:

These often rely on JWT as the underlying format, but they adhere to additional rules set forth by the OpenID Connect specification. They’re especially useful for federated identity scenarios where you have multiple applications trusting the same identity provider.

Opaque Tokens:

Sometimes you have tokens that look like random strings. They don’t contain self-describing claims in a readable or standard format. The application that issues them can store the details in a server-side session or database, so they’re not as large in payload. They can be simpler to start with, especially for service-to-service communication, though they might not have built-in signatures or be as flexible for advanced use cases.

Machine Identity Tokens / API Keys:

When it comes to machine-to-machine interactions, you’ll see tokens that might be long-lived API keys. These can be JWT-based or opaque. The key concept is that they represent a service or application rather than a human user.

Key Benefits of Using Identity Tokens

If you look at identity tokens in practice, one big advantage is that they simplify authentication across multiple services or applications. Instead of building separate login systems each time, you rely on a single identity provider. That identity provider issues a token, and suddenly all your services know how to trust that user or machine without juggling credentials.

It’s a straightforward way to centralize authentication while keeping each piece of your software relatively independent.

Another great benefit of identity tokens is how seamlessly they work with established standards—JWT, OpenID Connect, or OAuth 2.0. Sticking to those standards allows you to tap into a wide range of libraries and tools, cutting down on custom code.

There’s also the whole single sign-on angle, which lets users log in once and carry that authentication anywhere they need to go. It’s a better experience, plain and simple, and it reduces the friction of forcing someone to log in again and again.

At the same time, this approach can be a lifesaver when you’re scaling up microservices. That’s because each service checks the token independently rather than making repeated calls to a central authority.

That said, it’s important you are mindful of an important tradeoff -

Tokens with lifespans that are too short mean constantly hitting your identity system for renewals, meaning you might be stuck without a quick way to invalidate it if you need to revoke access.

Yet still, with their wide use across applications, tokens save you the headache of dealing with passwords and session IDs at every layer of your app. They keep your architecture more flexible, and they give you a consistent way to handle identities - both human and machine.

In other words, they do a lot of heavy lifting in authentication so you can focus on building out the rest of your software.

Common Misconceptions and Pitfalls

Having discussed the benefits, here are some of the common mistakes I’ve witnessed coming up time and time again:

Treating Tokens as a One-Stop Authorization Shop

I often encounter the following assumption:

“If the user’s identity is in the token, and I have their roles or scopes, I might as well do all my authorization decisions based on that.”

The problem is that these tokens are meant to verify who the user or service is, not to manage every facet of what they can do at a fine-grained level. If you put entire permission sets or complicated state data into a token, you’re forcing a re-issuance of the token every time something changes. That’s not realistic for a dynamic environment, and it’s definitely not secure.

Shoving Too Much Information into a Token

Tokens have practical limits on size. Some identity providers or networks even place limits on header sizes. Once you load your token with all sorts of claims (URLs, location data, or entire user objects), you might blow past those limits. Even if you don’t, you’ll end up with complexity that’s painful to manage.

Lifespan Extremes

A short-lived token might mean you’re validating everything on every request, hitting the identity provider too often, causing friction and performance bottlenecks. A long-lived token might stick around so long that you have no quick way to invalidate it if the user’s status changes. So you’re either locked into major performance overhead, or you risk giving out indefinite access.

Creating Separate Pipelines for Machine and Human Identities

Sometimes teams think machine identities (service-to-service tokens) deserve a completely different approach than human tokens. While there can be some differences, if you diverge too far, you’ll cause confusion, complexity, and potentially misaligned security policies.

Eventually, machine identities will behave more like human ones (especially as AI grows), so you might as well keep some consistency in how you handle them.

Best Practices for Implementing Identity Tokens

If you’re going to use identity tokens effectively, it’s key to keep some core best practices in mind:

Decouple Authentication and Authorization

I can’t stress this enough: let authentication focus on verifying who someone (or some service) is, and let authorization handle what they can do at any given moment.

That ensures you can change your authorization rules independently from your authentication flow. For instance, if you’ve got a payment status that needs to flip from active to canceled, you don’t want to rely on the identity token to convey that. You want a separate layer that can be updated in real-time.

Keep Tokens Lean

Only include essential identity-related claims in the token. If you need more dynamic or domain-specific data, store it elsewhere (like a user profile service or an authorization policy engine). The more bloat you add, the more often you’ll need to refresh tokens and the less flexible your system becomes.

Use Standard Protocols

OpenID Connect, OAuth 2.0, and JWT are well-understood and thoroughly documented. Leveraging these standards creates a broad ecosystem of libraries and tools, which makes integration and maintenance easier.

Balance Token Lifespan

Try to find a sweet spot between a token that’s too short-lived and causes performance overhead versus one that’s so long-lived that it’s risky. Often, this balance is context-dependent—what’s appropriate for a user login session might not be the same for a server-to-server API key.

Plan for Token Revocation

Even if your tokens are balanced in lifespan, you should have a strategy for invalidating them before they naturally expire. That might involve a token blacklist or a system that periodically checks the token status. If a user is deactivated or a service is compromised, you want a way to revoke that token swiftly.

How to Secure Identity Tokens

Securing identity tokens starts with how you send them.

If you’re not using HTTPS, you might as well be handing out free passes to anyone who can listen to your network traffic.

Another piece of the puzzle is where you store those tokens. In a browser, you might decide on HTTP-only cookies to limit exposure to JavaScript, or you could put them in local storage if you take extra precautions. In a mobile or desktop setting, you’ve got different storage considerations, but the principle stays the same: don’t let tokens end up in logs or the address bar, and definitely don’t make them easy to steal.

Once you’ve handled transport and storage, you need to verify signatures if you’re using JWTs. A lot of folks skim over that step, but it’s critical. If you don’t validate the token’s signature, you’re not really taking advantage of what makes tokens secure in the first place.

Then there’s token rotation, which can be a lifesaver if an attacker does manage to snag one of your tokens. By keeping tokens short-lived or periodically rolling them over, you limit how long an attacker can hang onto that access. If you decide on longer-lived tokens, a thorough strategy for revocation or re-rolling is essential so that you can cut off access quickly if something goes wrong.

To tie it all together, it’s wise to stay vigilant, watching logs for unusual activity and being ready to pull the plug on a token the moment it looks suspicious. When properly locked down like that, identity tokens deliver on their promise of making authentication smoother while keeping your system’s security under tight control.

Use Cases and Scenarios

To give these concepts a bit more background, here are some places where identity tokens make a lot of sense:

Single Sign-On Across Multiple Domains

You’ve probably encountered this if you’ve used a central login service that grants you access to several related apps. Rather than logging in separately each time, you get a token that each application trusts.

Mobile Applications

In a mobile app, once the user logs in, you don’t want them entering their credentials every time they open the app. A short- to medium-lived token can handle that, with periodic refresh through a backend service.

Machine-to-Machine (M2M) Communication

Services talking to each other can use tokens to identify themselves. This might be an opaque token or a JWT. You can store minimal claims that say, “Service A is authorized to call Service B,” or you might keep it simpler and rely on a separate authorization layer to figure out what each service is allowed to do.

Microservices in a Cloud Environment

I’ve seen a bunch of microservices each require an identity token to confirm requests are coming from a trusted source. This helps unify the trust model across all these services, so you don’t end up with inconsistent access checks.

Frequently Asked Questions (FAQ)

Q1: What’s the difference between an identity token and an access token?

In typical OAuth 2.0 or OpenID Connect usage, an “identity token” is meant to share information about the user’s identity, whereas an “access token” is used to call protected APIs.

In practice, we often see the terms blurred, and sometimes, an identity token can also carry access-related claims. But ideally, they serve distinct purposes.

Q2: Can I store entire user roles in the token?

Technically, you can store roles as claims, and many do. But if those roles are dynamic or need frequent updating, you’ll regret coupling them with the token’s lifespan.

A more flexible approach is to store roles in a dedicated user store or an authorization system that your application can check in real-time.

Q3: How long should I set the token expiration?

There’s no universal answer because it depends on your application’s security requirements and usage patterns. A rule of thumb is to keep short enough durations so you’re not giving indefinite access, but not so short that you hammer your authentication service on every request.

A few minutes to a few hours is common for user sessions, but machine tokens might differ.

Q4: Do I need a separate framework to manage token revocation?

It's highly recommended if you’re dealing with sensitive data or multiple microservices. Having a central store or an endpoint that tokens can be checked against is critical for scenarios like user deactivation or key compromise.

Q5: Are identity tokens only for web applications?

Absolutely not. While they’re very popular in web contexts, identity tokens can also be used by mobile apps, IoT devices, desktop applications, and, of course, service-to-service interactions.

Conclusion and Next Steps

In the end, identity tokens are fantastic at helping us verify who or what is accessing a particular resource. They let us simplify login flows, share trust across multiple services, and avoid direct handling of passwords.

But we can’t turn them into a cure-all - they have limits in capacity and practicality. If we try to use them to manage all the permissions, especially highly dynamic or time-sensitive data, we’re painting ourselves into a corner.

The best path is to decouple authentication from authorization. Keep your tokens lean, focus them on identity, and rely on a dedicated authorization layer for real-time access control decisions.

Whether it’s machine identities using long-lived tokens or human users relying on short-lived sessions, it pays to create a system that can evolve over time.

Looking ahead, we can anticipate that machine identities will multiply, especially as AI capabilities accelerate. This means that the separation of duties—authentication telling us who or what something is, authorization deciding what it can do—becomes even more critical.

Trying to update or expand your software while everything is mashed together in one token? That’s a surefire route to chaos.

If you want to stay nimble, adopt best practices such as policy as code and infrastructure as code. These approaches let you manage rules and infrastructure in a consistent way, often with the aid of automation. They also let you pivot quickly when the business demands it.

Today’s tokens won’t necessarily solve tomorrow’s issues, but building a flexible foundation means you don’t have to throw everything out when changes come knocking.

Reference Resources

Below are some useful resources to help you dig deeper:

• JWT Specification (IETF RFC 7519):
  Official documentation for JSON Web Tokens, explaining the structure (header, payload, and signature) and common claims.

• OpenID Connect Core Specification:
  The main specification details how ID tokens should be issued and validated and how they integrate with OAuth 2.0.

• OAuth 2.0 Framework (IETF RFC 6749):
  Explains the broader OAuth 2.0 authorization flows often paired with identity tokens in OpenID Connect.

• OWASP Cheat Sheet Series on JWT Security:
  Security best practices for token handling, protecting against CSRF, XSS, and safe storage.

• Why JWTs Aren’t Made for Authorization:
  A deep dive into the limitations of using JWTs for authorization logic.

• Introduction to OPAL (Open Policy Administration Layer):
  Learn how real-time policy updates can help you decouple authorization.

• Policy as Code Tools - Open Policy Agent (OPA):
  A leading open-source tool for policy-based control across your stack.

Feel free to consult these references for a deeper understanding of how tokens are structured, how they’re supposed to be used, and how to keep them safe. It’s important to remember that while identity tokens are a tremendous aid, they’re only one piece of your security puzzle.

Use them wisely, keep them focused on what they do best—verifying identity—and let specialized authorization layers handle the heavier lifting of deciding who can do what and when.

That’s the core lesson I’ve learned working with these systems for years: the more you respect the boundaries between authentication and authorization, the happier you’ll be. Keep your tokens lean, keep your architecture flexible, and your software will adapt to changes in requirements, threat models, or even the nature of the identities themselves—human or machine—without getting stuck in a rigid design.

Looking to learn more? Join our Slack community to ask any questions you may have and discuss authorization with other developers.