Quick summary
What it is: a developer who did not write your app reads its code and tells you, in writing, what is risky, what is fragile and what each problem would take to fix. A good audit covers security, how the code is organized, tests, the packages it depends on, the database and hosting.
What it costs: published prices run from about $2,500 for a focused audit of a small app to $18,000 to $45,000 for a full two-week audit by a development firm. Enterprise systems cost more.
What you should get: a report that ranks every finding by risk, shows the evidence and estimates the effort to fix it, plus a walkthrough in plain English.
How to choose: ask the four questions below, and pick an auditor who is not the team that wrote the code.
Code Audit Services at a Glance
| How you buy it | Published price | How long | Best for | Watch out for |
|---|---|---|---|---|
| Freelance senior developer | Flat fee, such as $3,500 on one Contra listing | About a week | A small app and a fast second opinion | Depth depends entirely on the person |
| Development firm audit | $2,500 to $8,000 focused, $18,000 to $45,000 full | 1 to 4 weeks | A larger codebase, or a report to show investors | An audit used to sell you a rebuild |
| Security firm | Average code security audit $11,400 (HackerOne) | Days to weeks | Payments, health or personal data, or a customer asking for a security test | Covers security, not whether the code is easy to change |
| Technical due diligence firm | Quoted per deal | Weeks | A fundraise or a sale of the company | Written for investors, not for fixing |
| Automated tools | Free to monthly | Minutes | A first pass on known vulnerabilities in your packages | A long list with no priorities or context |
| Development subscription | Flat monthly fee | A review request, then fixes one at a time | Founders who want the risky parts reviewed and fixed | The reviewer also does the fixes |
Before you hire anyone, ask these four questions:
- Question 1, "What exactly will you look at, and what won't you?" Get the scope in writing: which code, which areas (security, architecture, tests, hosting) and whether they will test the running app or only read the code.
- Question 2, "Can I see a sample report?" Look for severity ratings, evidence for each finding and an effort estimate to fix it. A list of tool warnings is not an audit.
- Question 3, "How will you rank what you find?" You want the findings ordered by risk to your business and cost to fix, so you know what to do first and what can wait.
- Question 4, "Are you also selling me the fix?" Fora Soft, a firm that sells audits, says the auditor "has to be independent of the team being audited." If the auditor would also do the work, ask for evidence on every finding, and keep the right to take the report elsewhere.
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This guide is for founders who have an app and cannot tell whether its code is any good. If the project has already stalled or the developer has gone, start with software project rescue. If an AI tool built it and it keeps breaking, see vibe coding cleanup.
What a Code Audit Covers
An audit is a structured read of your code against a checklist. The areas below are what most providers cover, in roughly the order a founder should care about them.
Security and access
Can one customer see another customer's data? Are logins, passwords and payments handled safely? Are API keys and passwords written into the code? OWASP, the open security project, ranks broken access control first in its 2025 Top 10 and found some form of it in 100% of the applications tested.
Architecture
How the app is put together, and whether it can take more users and more features without a rewrite.
Code quality
Whether a new developer could read and change the code safely: duplication, very long files, dead code, and naming that hides what things do.
Dependencies
The outside packages the app is built on. Old versions with known vulnerabilities, abandoned packages, and licenses that conflict with selling your product.
Tests
Whether automated tests exist, whether they run on every change, and whether they cover the parts that make you money, like sign-up and billing.
Database and data
How data is stored, whether backups exist and have been restored at least once, and whether queries will slow down as you grow.
Hosting and deploys
How code gets from a developer's laptop to your live app, who has access, and whether the accounts belong to your company.
Documentation and handover
Whether anyone other than the original developer could run, deploy and fix the app tomorrow.
What the Audit Report Should Include
The report is the product you are buying. Before you pay, make sure it will contain these.
- A one-page summary in plain English: how healthy the code is and the three things to fix first.
- Every finding with a severity rating, such as critical, high, medium or low.
- Evidence for each finding: the file and line, or the steps to reproduce the problem.
- What each problem could lead to, in business terms: leaked data, downtime, slower releases.
- An effort estimate to fix each finding, in hours or days.
- A fix plan in order, most serious first, with what can safely wait.
- A live walkthrough where you can ask what anything means.
The report belongs to you. Put that in writing, so you can hand it to any developer, investor or buyer.
What Code Audit Services Cost
Published prices come almost entirely from firms that sell audits, so treat them as rough. They do show how much scope moves the price.
| Who | What is included | Published price | How long |
|---|---|---|---|
| A freelance listing on Contra | Senior read of the codebase, 20 to 25 page report, fix estimates, 60-minute walkthrough | $3,500 flat | 5 days |
| Acquaint Soft, a development firm | A focused architecture review or code audit | $2,500 to $8,000 | 2 to 4 weeks |
| HackerOne, a security company | The average cost of a code security audit, from its 7th Hacker-Powered Security Report | $11,400 | Not stated |
| Fora Soft, a development firm | A full 12-section audit with two auditors and a 30 to 60 page report | $18,000 to $45,000 | 10 to 14 days |
| Fora Soft | An enterprise audit with a team | $70,000 to $180,000 | 3 to 5 weeks |
What moves the price:
- The size of the codebase. One small web app is days of reading. Several services, a mobile app and years of history is weeks.
- How deep the security work goes. Reading code for security issues is one thing. Actively attacking the running app, called penetration testing, is a separate service and often a separate firm.
- Who the report is for. A report you will use to fix things can be short and direct. One written for investors or a buyer takes longer and costs more.
For comparison, hiring someone to do this in-house means a salary: the US Bureau of Labor Statistics puts the median software developer's pay at $135,980 a year, before benefits.
When You Need a Code Audit
Most founders order an audit at one of these moments:
- Your developer or agency is leaving, or has gone quiet. Find out what you own and what state it is in before you lose the person who knows it.
- An AI tool built most of the app. It may work in a demo and still be unsafe with real customers.
- Every change breaks something else. That is usually a sign of missing tests and tangled code, and an audit shows where.
- Before a fundraise or a sale. Investors and buyers may run technical due diligence anyway. Finding the problems first lets you fix them, or at least explain them.
- Before a big new feature or a new developer. Building on a weak part of the app makes the problem more expensive later.
- A customer sends a security questionnaire. Larger customers often ask how you handle their data. An audit tells you whether the honest answer is a good one.
Why Problems in Code Get Expensive
Bad code rarely fails all at once. It slows down every change: Stripe's survey put the time lost to "bad code" alone at about four hours a week per developer. At the scale of a whole country, CISQ, a software quality consortium, estimates the accumulated technical debt in US software at about $1.52 trillion. Technical debt is the cost of reworking shortcuts taken earlier.
Leaked secrets are the quickest way for a small app to get hurt. GitGuardian found that 70% of the secrets leaked in 2022 were still active when it published its 2025 report, meaning anyone who found them could still use them. An audit should find keys written into the code and tell you to change them.
Code Audit vs Code Review vs Security Audit
These names get mixed up, and providers use them loosely. Ask what you are actually getting.
| Service | What it looks at | When | What you get |
|---|---|---|---|
| Code review | Each change before it is added to the app | Every day, as part of development | Comments on that change |
| Code audit | The whole codebase: security, structure, tests, dependencies, hosting | Once, at a key moment | A ranked report and a fix plan |
| Security audit or penetration test | Security only, often by attacking the running app | Before launch, yearly, or when a customer asks | Vulnerabilities with proof and fixes |
| Technical due diligence | The code plus the team, process, costs and risks to a deal | During a fundraise or sale | A report for investors or a buyer |
If no one reviews changes before they go live today, an audit will tell you what has built up. Adding code review afterwards stops it building up again.
What You Can Check Yourself First
You do not need to read code to answer some of the most important questions. Do these before you pay anyone, and send the answers to the auditor.
- Who owns the accounts? The code repository, hosting, domain, database and payment accounts should all be in your company's name. Our guide to software development contracts covers getting the code assigned to you in writing.
- Can you get in? Make sure you, not only the developer, can log in to each of those accounts.
- Is there a backup? Ask when the database was last backed up, and whether a backup has ever been restored.
- Run the free checks. Tools such as npm audit and GitHub's Dependabot alerts compare the packages your app uses against databases of known vulnerabilities. They find old, unsafe packages. They cannot find a customer seeing someone else's data.
How to Choose a Code Audit Provider
Often the quickest and cheapest. Ask what they have built and audited before, and for a sample report.
More people and a more formal report. Check how much of the report points to work they want to sell you.
The deepest security work, including penetration testing. It will not tell you whether the code is easy to build on.
A flat monthly fee for requests worked one at a time. A review is one request, and the fixes follow as more requests. See developer as a service.
To compare the firms themselves, see how to choose a software development company.
Red Flags in a Code Audit Proposal
- No written scope. You cannot tell later whether something was missed or never looked at.
- No sample report. Or a sample that is a printout from an automated tool.
- Findings with no evidence. Every problem should point to a file, a line or steps you can repeat.
- "Rebuild everything" before anyone has read the code. A rebuild is sometimes right. It should be the conclusion of the audit, not its starting point.
- No effort estimates. Without them you cannot plan or budget the fixes.
- They want to keep the report. It is your code and your report.
After the Audit: Fix, Rebuild or Leave It
The report is only worth what gets fixed. For each finding, you will usually choose one of three things:
- Fix it now. Anything critical: data one customer can see that belongs to another, leaked keys, missing backups. Do these first, before new features.
- Fix it as you go. Messy code in parts you are about to change anyway. Clean it up as part of that work, with tests, so it stays fixed.
- Leave it. Ugly code in a part that works and rarely changes can wait. The audit should say so.
Rebuilding a part of the app makes sense when fixing it would cost more than replacing it, which a good auditor will estimate for you. For what ongoing upkeep looks like after the fixes, see software maintenance services.
How StackTie Fits
StackTie is a development subscription, not an audit firm. You send requests, they are worked one at a time, and each one comes back in days as a pull request with a plain-English summary of what changed and why. If you are not sure your code is any good, the first request can be a review of the part that worries you most, such as logins and who can see which data, written up in plain English with what each fix would take. The fixes then follow as requests, most serious first. We did not write your code, so we have no earlier work to defend, but we would also do the fixes, so ask us for evidence on every finding, as you would anyone else. One senior developer, Michael, leads every build, and everything we build belongs to your company and lives in your own accounts. There is a money-back guarantee if it is not a fit. If you need a formal audit report for investors or a security certification, a dedicated audit or security firm is the better choice, and the subscription is not for native iOS or Android apps or a whole team working in parallel. The price and what is included are on the homepage.
