YAML Merge Tool
Deep-merge two YAML files with configurable key conflict resolution using our free yaml merge tool. Paste a Base YAML and an Override YAML, choose how conflicts and sequences are handled — overwrite, preserve, concat, union, or error on conflict — and get the merged result instantly with a key-by-key diff summary. Perfect for Kubernetes manifests, Helm values, Docker Compose overrides, and CI/CD configs. All processing runs locally in your browser — no signup required.
Paste two YAML documents below. The Base YAML is the starting document; the Override YAML is merged on top of it. Configure the merge strategy to control how key conflicts and sequences are handled. All processing runs locally in your browser — no signup required.
How to handle conflicting keys
Why Use Our YAML Merge Tool?
Instant YAML Deep Merge
Our yaml merge tool deep-merges two YAML documents instantly in your browser. Nested mappings are recursively merged, sequences are handled by your chosen strategy, and the result is ready to copy or download in milliseconds — no waiting, no server calls.
Secure YAML Merge Online
All yaml merge processing happens locally in your browser using JavaScript. Your YAML data — including API keys, credentials, and configuration secrets — never leaves your device, ensuring 100% privacy every time you use our yaml merge tool online.
No File Size Limits
Merge large YAML documents without restrictions. Our yaml merge tool handles any size input — from small config snippets to large Kubernetes manifests. There are no artificial size limits, upload restrictions, or premium tiers.
100% Free Forever
Use our yaml merge tool completely free with no limitations. No signup required, no hidden fees, no premium tiers, no ads — just unlimited, free yaml merge operations whenever you need them. The best free yaml merge tool online.
Common Use Cases for YAML Merge Tool
Configuration Override Patterns
Merge a base YAML configuration with environment-specific overrides. Use the Overwrite strategy to let production, staging, or development configs override base values while inheriting all unspecified settings from the base document.
Kubernetes Manifest Merging
Combine base Kubernetes YAML manifests with environment-specific patches. Our yaml merge tool deep-merges nested mappings like spec, containers, and env sequences, making it easy to manage multi-environment deployments without duplicating entire manifests.
Helm Values Merging
Merge default Helm values.yaml with environment-specific overrides. Use the Preserve strategy to ensure default chart values are never accidentally overwritten, or Overwrite to let environment-specific values take full precedence over chart defaults.
Infrastructure as Code Patching
Apply patches to Terraform, Ansible, or Pulumi YAML configurations. Use the Error on Conflict strategy to catch unintended overwrites before they reach your infrastructure, preventing accidental configuration drift in production environments.
CI/CD Pipeline Config Merging
Merge base GitHub Actions, GitLab CI, or CircleCI YAML workflows with project-specific extensions. Our yaml merge tool handles nested mappings like jobs, steps, and environment variables correctly, making pipeline reuse straightforward.
Docker Compose Override Merging
Combine docker-compose.yml base files with docker-compose.override.yml files. Use the Concat sequence strategy to merge service lists and volume arrays, or Overwrite to let override values replace base service definitions entirely.
Understanding YAML Deep Merge
What is YAML Deep Merge?
YAML deep merge is the process of combining two YAML documents recursively — merging nested mappings at every level rather than simply replacing top-level keys. A shallow merge only merges the top level, so nested mappings in the override completely replace nested mappings in the base. A deep merge recurses into nested mappings, merging their keys individually. Our yaml merge tool performs a full deep merge with configurable strategies for handling key conflicts and sequences — all running locally in your browser with no server uploads required.
How Our YAML Merge Tool Works
- Input Your YAML Documents: Paste the Base YAML (the starting document) and the Override YAML (the document to merge on top) into the two input panels. Upload .yaml or .yml files directly using the Upload buttons. A sample configuration merge is preloaded so you can explore the tool immediately.
- Configure the Merge Strategy: Choose how key conflicts and sequences are handled — Overwrite (override wins), Preserve (base wins), Concat sequences (join sequences), Union sequences (join without duplicates), or Error on Conflict (throw on any conflict). The strategy applies recursively to all nested levels of both documents.
- Copy or Download the Result: The merged YAML appears in the output panel with a merge summary showing added, overwritten, and preserved keys. Copy to clipboard or download as a .yaml file. All processing runs locally — your data never leaves your device.
What Gets Merged During YAML Merge
- Scalar values (strings, numbers, booleans, null): Resolved by the configured strategy — Overwrite replaces the base value with the override value; Preserve keeps the base value unchanged.
- Nested mappings (objects): Always recursively merged at every nesting level. Keys present only in the base are preserved; keys present only in the override are added; conflicting keys are resolved by the strategy.
- Sequences (arrays): Handled by the sequence strategy — Concat joins both sequences, Union joins without duplicates, Overwrite replaces the base sequence, Preserve keeps the base sequence.
- New keys from override: Any key present in the Override YAML but absent from the Base YAML is always added to the merged output, regardless of the strategy chosen.
Deep Merge vs. Shallow Merge in YAML
The key difference between deep and shallow merge is how nested mappings are handled. With a shallow merge, if both documents have a configkey, the override's config mapping completely replaces the base's — losing any base config keys not present in the override. With a deep merge, the two config mappings are themselves merged recursively, so base config keys are preserved unless explicitly overridden. Our yaml merge tool always performs a deep merge, recursing into all nested mappings at every level of both YAML documents.
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Frequently Asked Questions About YAML Merge Tool
A yaml merge tool combines two YAML documents into one by recursively merging their keys and values. Our yaml merge tool performs a deep merge — nested mappings are merged at every level, not just the top level. It runs entirely in your browser with no server uploads, and supports five configurable merge strategies for handling key conflicts and sequences.
A shallow merge only merges the top-level keys — if both documents have a nested "config" mapping, the override's config completely replaces the base's config. A deep merge recurses into nested mappings, merging their keys individually so base config keys are preserved unless explicitly overridden. Our yaml merge tool always performs a deep merge.
Use Overwrite when you want override values to take precedence at every conflict — this is the most common strategy for environment-specific configs. Use Preserve when the base document contains authoritative defaults that should not be changed. Use Concat or Union for sequence fields that should be combined rather than replaced. Use Error on Conflict to catch unintended overwrites before they cause problems in production.
By default (Overwrite strategy), sequences at the same key are replaced by the override sequence. Choose Concat to join both sequences, or Union to join them with duplicates removed. The sequence strategy applies to all sequences in the YAML at every nesting level.
Absolutely. All yaml merge processing happens locally in your browser using JavaScript. Your YAML data — including API keys, credentials, Kubernetes secrets, and configuration values — is never sent to any server, stored, or logged. Your data stays completely private on your device every time you use our yaml merge tool online.
Yes. Our yaml merge tool is well-suited for merging Kubernetes YAML manifests. Paste your base manifest and your environment-specific patch, choose the Overwrite strategy for most cases, and get the merged manifest ready to apply. The deep merge ensures nested fields like spec.containers and metadata.labels are merged correctly rather than replaced entirely.
Yes. Both the Base YAML and Override YAML panels have an Upload button that accepts .yaml and .yml files. The file content is loaded into the input panel and you can then click Merge YAML to process it. All file reading happens locally in your browser — no files are uploaded to any server.
When a key exists in both documents but with different types (e.g., a string in the base and a mapping in the override), the merge tool treats it as a scalar conflict and applies the configured strategy — Overwrite replaces the base value, Preserve keeps it, and Error on Conflict throws an error with the conflicting path.
Yes! Our yaml merge tool is 100% free with no signup, no account, and no usage limits. Merge YAML documents as many times as you need — completely free, forever. No premium tier, no ads, no file size restrictions.