PERFORMANCE

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Performance Budget

/pərˈfɔːrməns ˈbʌdʒɪt/n.

Filed underPerformanceArchitecture

In brief · quick answer

A set of agreed-upon limits on performance metrics or resource quantities that a team commits not to exceed. Prevents regressions from shipping.

§ 1 Definition

A performance budget is a contract among developers, designers, and stakeholders setting hard limits on performance. Budgets can be quantity-based (max 300 KB JS, max 50 HTTP requests) or metric-based (LCP under 2.0 s). Enforced in CI/CD to block deploys exceeding limits.

§ 2 Why Budgets Matter

Every new feature adds weight. Without a budget, teams accumulate bloat until the site is slow. A budget forces tradeoffs upfront: 'Add this library, but remove something equal in weight.'

§ 3 Common Misunderstandings

Budgeting only page weight is insufficient. A 200 KB page can have 500 ms of main thread blocking. Budget both quantity and metric dimensions. Budgets need periodic review.

§ 4 Implementation

Use Lighthouse CI with budget assertions, bundlesize, or webpack performance hints. Define budgets in version control. Fail CI on budget exceedance.

§ 5 Note

Starting point: 300 KB JS, 100 KB CSS, 2 MB images, under 50 requests.

§ 6 In code

{
  "ci": {
    "assert": {
      "assertions": {
        "categories:performance": ["error", {"minScore": 0.9}],
        "resource-summary:script:size": ["error", {"maxNumericValue": 300000}]
      }
    }
  }
}

§ 7 Common questions

Q. What if we need to exceed budget?: A. Discuss deliberately. A budget is a baseline, not a wall.

Key takeaways

Enforceable limit on metrics/resources.
Prevents gradual bloat.
Budget both quantity and metrics.
Enforce in CI/CD.

How Atomic Glue helps

Atomic Glue helps define and enforce performance budgets with Lighthouse CI. Web Development services.

Get in touch

# Performance Budget

A set of agreed-upon limits on performance metrics or resource quantities that a team commits not to exceed. Prevents regressions from shipping.

Category: Performance (also: Architecture)

Author: Atomic Glue Performance Team

## Definition

## Why Budgets Matter

Every new feature adds weight. Without a budget, teams accumulate bloat until the site is slow. A budget forces tradeoffs upfront: 'Add this library, but remove something equal in weight.'

## Common Misunderstandings

Budgeting only page weight is insufficient. A 200 KB page can have 500 ms of main thread blocking. Budget both quantity and metric dimensions. Budgets need periodic review.

## Implementation

Use Lighthouse CI with budget assertions, bundlesize, or webpack performance hints. Define budgets in version control. Fail CI on budget exceedance.

## Note

Starting point: 300 KB JS, 100 KB CSS, 2 MB images, under 50 requests.

## In code

{
  "ci": {
    "assert": {
      "assertions": {
        "categories:performance": ["error", {"minScore": 0.9}],
        "resource-summary:script:size": ["error", {"maxNumericValue": 300000}]
      }
    }
  }
}

## Common questions

Q: What if we need to exceed budget?

A: Discuss deliberately. A budget is a baseline, not a wall.

## Key takeaways

Enforceable limit on metrics/resources.
Prevents gradual bloat.
Budget both quantity and metrics.
Enforce in CI/CD.

## Related entries

Last updated July 2026. Permalink: atomicglue.co/glossary/performance-budget