Recommended free tool combination: Google Keyword Planner (provides search volume ranges like “1K-10K”) and Google Trends (popularity 0-100 score). Paid tools: choose Ahrefs (starting at $99/month, 10 billion keyword database, precise search volume) or SEMrush (starting at $129.95/month, 140 million keywords + competitor analysis). For long-tail keywords, use AnswerThePublic (free version limited).
Free Tools (Suitable for Limited Budgets or Initial Research)
In Google keyword research, free tools can provide basic data, but each has limitations. Google Keyword Planner (requires binding a Google Ads account) shows search volume as ranges (like “100-1K”) rather than precise numbers, and ad competition data is more skewed toward paid search.
Google Trends is free but only shows relative popularity (0-100 score) without actual search volume, making it suitable for observing trends rather than quantitative analysis.
Ubersuggest free version limits you to 3 queries per day but provides keyword difficulty (SEO Difficulty) and CPC (cost per click) estimates, suitable for quick reference.
AnswerThePublic excels at mining long-tail question keywords (queries starting with “how to” or “best”), but the free version only shows partial results; full data requires payment ($99/month).
If budget is limited, consider combining these tools—for example, using Google Trends to find trending keywords, then Ubersuggest to check search volume, and finally AnswerThePublic to supplement question-type keywords.
Google Keyword Planner
Google Keyword Planner was originally designed as a keyword research tool for Google Ads users, but can also be used for SEO. Its biggest advantage is that data comes directly from Google searches, but the drawback is obvious: search volume is displayed as ranges (like “1K-10K”) rather than specific numbers, making precise keyword comparison difficult.
Its “competition level” metric is based on ad bidding intensity, not natural search ranking difficulty, so its value for SEO is limited.
However, it still provides useful information such as monthly average search volume ranges and recommended bid ranges (CPC), suitable for initial screening of high-potential keywords. Note that you must register for a Google Ads account (no need to actually run ads) to view complete data.
Google Trends
Google Trends is a free trend analysis tool that shows how keyword popularity changes over time and across regions, but does not provide actual search volume.
Its data is presented as “relative popularity” on a 0-100 scale, suitable for comparing the popularity of multiple keywords (e.g., “iPhone vs Samsung”). A practical tip is to use the “related queries” feature to see what other terms users search for, which helps expand your keyword database.
For example, searching “yoga mat” might reveal derivative terms like “non-slip yoga mat” and “thick yoga mat.” Google Trends also supports regional filtering, suitable for localized SEO research, such as analyzing search differences for a term in the US versus UK.
Ubersuggest
Ubersuggest was developed by SEO expert Neil Patel. The free version provides keyword search volume, SEO difficulty scores, and CPC estimates, but limits you to 3 queries per day; exceeding this requires upgrading ($29/month and up).
Its data sources include Google Keyword Planner and third-party crawlers, so search volume is more specific than Google Trends (showing “2,400” for example rather than a range).
SEO difficulty scores (0-100) help judge keyword competition intensity, but note that this score is based on page authority (Domain Authority) and backlink counts rather than actual ranking difficulty.
Ubersuggest also offers a “content ideas” feature that lists top-ranking web pages for reference on competitor content structure.
AnswerThePublic
AnswerThePublic specializes in mining question-type keywords that users actually search for (like “how to fix a leaky faucet” or “best running shoes for flat feet”), which typically have lower competition and are suitable for long-tail SEO strategies.
The free version shows partial results, but complete data (including search volume) requires payment ($99/month). Its data comes from Google autocomplete and related searches, reflecting real users’ search intent.
For example, entering “coffee maker” might yield practical questions like “how to clean a coffee maker” and “which brand of coffee maker is best.” These keywords have higher conversion rates because users searching them often have clear needs.
However, AnswerThePublic doesn’t provide search volume data; you’ll need to combine it with Google Keyword Planner or Ubersuggest for further analysis.
Paid Tools (Suitable for In-depth Optimization or Business Needs)
Compared to free versions, paid keyword tools’ core advantages include providing precise search volume data(Ahrefs accurate to the unit)more comprehensive competition analysis (including natural search and paid ads), and long-term historical data tracking (SEMrush can view 5-year keyword trends).
Taking Ahrefs as an example, its database contains over 10 billion keywords, updates search volume data monthly, and indicates click-through rate (CTR) for each keyword.
SEMrush covers 140 million keywords, particularly suitable for analyzing competitor keyword strategies, directly showing competitors’ top 100 keywords and their traffic share.
Moz Pro has a smaller keyword database (around 500 million) but provides unique “keyword difficulty” scores (0-100), helping quickly determine optimization feasibility.
Paid tools typically start at $130/month, suitable for teams with steady content output or advertising budgets.
Ahrefs
Ahrefs’ keyword database contains over 10 billion keywords, updates search volume data monthly, and provides search volume precise to the unit (like “2,450 times/month” rather than a range).
Beyond basic search volume, Ahrefs also provides click-through rate (CTR) data, showing the actual click distribution for a keyword in search results (for example, results ranking #1 typically receive 30%-40% of clicks).
Another core feature is “keyword gap analysis” (Keyword Gap), which compares keyword overlap across multiple competitors, quickly identifying terms you’re not covering but competitors are ranking for. For example, if three competitors are all ranking for “best wireless headphones” but your site has no relevant page, that’s an obvious optimization opportunity.
Ahrefs’ “Content Explorer” can also analyze high-performing content across the web, such as filtering articles about “coffee maker” that received the most backlinks in the past year, providing direction for content creation.
However, Ahrefs has a higher starting price (starting at $99/month), and its features may be overly complex for beginners, making it more suitable for professional SEO teams or businesses committed to long-term content marketing.
If you’re interested in this tool, you may read: What is Ahrefs used for? | Monthly $129/249/449/14990 Membership Purchase Guide
SEMrush
SEMrush’s keyword database covers 140 million keywords and provides the “Keyword Magic Tool“, which can generate hundreds of long-tail keyword variations with one click (for example, searching “running shoes” yields derivative terms like “best running shoes for flat feet” and “women’s running shoes 2024”).
SEMrush’s “competitor keyword analysis” feature is particularly powerful, allowing you to directly view competitors’ top 100 keywords and indicating estimated traffic share for each term. For example, when analyzing a fitness equipment website, you might discover that 30% of its search traffic comes from terms related to “home gym equipment”, suggesting you should prioritize optimizing similar keywords.
SEMrush also provides a “historical data” feature, allowing you to view a keyword’s search volume trends over the past 5 years, helping judge seasonal fluctuations or long-term demand changes.
However, SEMrush’s pricing is slightly higher than similar tools (
If you’re interested in this tool, you may read: Ubersuggest vs SEMrush vs Ahrefs SEO Usage Review | Features/Data/Pricing
Moz Pro
Moz Pro’s keyword database scale (around 500 million) is smaller than Ahrefs and SEMrush, but its “keyword difficulty” (Keyword Difficulty, KD) scoring system is more friendly for small and medium enterprises and individual webmasters.
KD scores (0-100) comprehensively consider the domain authority (DA) and backlink counts of top-ranking pages, quickly judging a term’s competition intensity. For example, keywords with KD scores below 30 are usually easier to rank for, while those above 70 may require substantial backlink support.
Moz Pro’s “rank tracking” feature can monitor daily ranking changes for multiple keywords, comparing your position with competitors. Another practical feature is “page optimization suggestions” (On-Page Grader), which automatically checks page elements like title, description, and content structure based on target keywords, providing an optimization score (e.g., 85/100).
However, Moz Pro’s search volume data updates less frequently (approximately quarterly), and it doesn’t provide click-through rate analysis, making it unsuitable for ad optimization requiring real-time data.
Its starting price is $99/month, comparable to Ahrefs, but its features are more geared toward basic SEO.
Keyword Tool
Keyword Tool’s core feature is generating massive long-tail keywords based on Google autocomplete, particularly suitable for non-English market SEO research. It supports keyword queries in over 190 languages (including Chinese, Spanish, Arabic, etc.) and displays estimated search volume for each term (data sources include Google Keyword Planner and third-party databases).
For example, searching “coffee maker” yields specific queries like “家用咖啡机推荐” (home coffee maker recommendations) and “全自动咖啡机价格” (fully automatic coffee maker price), with search volume annotations (for example, “家用咖啡机推荐” has a monthly average of 1,200 searches). Keyword Tool also provides “questions” and “prepositions” categories, such as “how to use a French press” or “coffee maker vs espresso machine”, which typically have clear user intent.
However, Keyword Tool’s search volume data precision is lower than Ahrefs or SEMrush (some terms only show “<10" or "10-100"), and it lacks competition analysis features. Its professional version starts at $69/month, suitable for content teams needing multi-language support or focusing on long-tail keywords, but it’s recommended to combine with other tools (like Google Keyword Planner) to verify data accuracy.
How to Choose the Right Tool?
When selecting a keyword research tool, core considerations include budget (free tools like Google Keyword Planner vs. paid tools like Ahrefs’ ), data precision (ranges like “1K-10K” vs. precise numbers like “2,450”), and use case (SEO, advertising, or multi-language support).
50, the free tools combination (
500+ keyword rankings or analyze competitor strategies, paid tools like
Google Keyword Planner updates monthly, while Ahrefs’ keyword database refreshes daily, suitable for scenarios requiring real-time data.
Choose by Budget
Free tools are suitable for limited budgets or initial research, but their features are clearly limited. For example, Google Keyword Planner only shows broad search volume ranges (like “100-1K”) without logging into a Google Ads account, while paid tools like Ahrefs can provide data precise to the unit (like “1,250 times/month”).
Free tools’ query limits are also problematic: Ubersuggest free version limits you to 3 queries per day, while the paid version () removes restrictions and opens more data dimensions (like click-through rate estimates).
$50-$100/month,
For enterprise users, consider team collaboration costs—for example, SEMrush’s “Business” plan ($499/month) supports 5 users sharing, which is more cost-effective than purchasing multiple individual accounts.
Choose by Data Needs
If you only need basic search volume, Google Keyword Planner or Ubersuggest is sufficient;
but if you need to analyze long-term keyword trends, SEMrush’s 5-year historical data feature is more practical (for example, judging whether “air fryer” has seasonal fluctuations).
Moz Pro’s “keyword difficulty” scores (0-100) are based on domain authority, while Ahrefs’ “keyword difficulty” also comprehensively considers the backlink counts of homepage results.
For content teams, Ahrefs can show the actual click distribution for a keyword in search results (for example, the #1 position averages 35% of clicks), while free tools provide no such functionality. If you’re targeting multilingual markets, Keyword Tool supports keyword generation in 190 languages, but search volume data should be cross-verified with Google Keyword Planner.
Choose by Use Case
- SEO Optimization: Prioritize tools providing comprehensive competition analysis, such as Ahrefs’ “keyword gap” feature or SEMrush’s “competitor keyword comparison.” For example, if you discover that 30% of a competitor’s top 10 keywords are irrelevant to your site, you can specifically optimize those terms.
- Advertising (Google Ads): Google Keyword Planner is essential as it directly integrates ad competition data and suggested bids (CPC), while SEMrush’s “advertising research” module can also analyze competitors’ ad copy and historical campaign strategies.
- Content Creation: AnswerThePublic or Keyword Tool’s question keyword mining features are more practical, such as generating long-tail terms like “how to repair a leaking faucet,” then filtering through Ahrefs for keywords with >500 search volume to prioritize for content creation.
Moz Pro can integrate with WordPress plugins to automatically optimize pages, while SEMrush supports Google Analytics data import, directly linking keywords to actual traffic performance.
